AGILE is a collection of techniques and approaches that improves decision-making, productivity, and thinking skills within your team.
All aspects of traditional software engineering, such as project management, software design and architecture, and process optimization, are covered by these techniques. To make them as simple to implement as feasible, they are composed of procedures that have been streamlined and optimized.

Because an appropriate mindset can significantly impact how well a team applies the techniques, AGILE is also a mindset. This mindset facilitates information sharing among team members so that important project choices can be made collectively rather than by a manager acting as the decision-maker in isolation. Embracing an agile mentality involves including the entire team in planning, design, and process optimization. Every member of an agile team participates in the application of the techniques and shares the same information as the group as a whole.

For many teams that have not experienced as much success, agile has turned out to be very different from what it promised, and a big part of that variance is frequently the attitude the team brings to every project. Most software development businesses have dabbled in agile, and while many of them have found success, some teams have produced less-than-ideal outcomes. They’ve made some progress in how they run their projects—enough to make the effort to embrace agile worth it—but they haven’t seen the major changes that they feel agile promised them. This is the main idea behind the mentality shift: "going agile" refers to assisting the team in developing a productive mindset.
However, what exactly does "mindset shift" mean? Working on a software team entails planning, designing, developing, and releasing software on a daily basis. What connection does "mindset" have to that? It turns out that how you and your teammates approach them affects a lot of the procedures you employ in your day-to-day work.
Here's an illustration. The daily standup, a gathering when team members discuss their goals and issues, is one of the most popular agile methods used by teams. We keep the meeting brief by having everyone stand the entire time. Adding a daily standup to a project has shown to be quite successful for numerous teams.

Understanding Agile values(Agile manifesto)

• Individual and interactions over processes and tools
• Working software over comprehensive documentation
• Customer collaboration over contract negotiation
• Responding to change over following a plan

KEY POINTS ON AGILE VALUES

• The Agile Manifesto contains common values and ideas that lead to effective teams.
• “Individuals and interactions over processes and tools” means the team should focus on the people on the team and how they communicate first, and the tools and practices that they use second.
• “Working software over comprehensive documentation” means that delivering software that does what users need is more important than delivering a specification that describes it.
• Working software means software that delivers value to the company.
• “Customer collaboration over contract negotiation” means treating everyone like they’re on the same team.
• Many effective agile teams treat the product owner as a member of the project team to collaborate with, rather than a client or customer to negotiate with.
• “Responding to change over following a plan” means recognizing that plans become inaccurate, and that it’s more important to deliver the software than it is to work the plan.
• A task board is an agile planning tool in which user stories are attached to a board and categorized into columns based on their status in the current project or iteration.

The 12 Principles of Agile Software

1. Our highest priority is to satisfy the customer through early and continuous delivery of valuable software- The customer is always right.

2. Welcome changing requirements, even late in development. Agile processes harness change for the customer’s competitive advantage. It means:
   a. Nobody gets in "trouble" when there's a change.
   b. We're all in this together.Everybody is collaborating.
   c. We don't sit on change until it's too late.
   d. We stop thinking of change as mistakes.
   e. We learn from the changes. This is the most effective way for a team to grow and get better at building software together.

3. Deliver working software frequently, from a couple of weeks to a couple of months, with a preference to the shorter timescale. By using time-boxed iteration to deliver working software frequently, agile teams constantly adjust the project so that it delivers the most value to the customer

4. The most efficient and effective method of conveying information to and within a development team is face-to-face conversation. When people on the team don't communicate on a face to face basis, they may agree on the broad strokes, but end up working toward different goals. Comprehensive documentation can make this worse by making it easy to introduce ambiguity.

5. Collaboration between business analysts and developers on a daily basis throughout the project yields greater efficiency. This is due to the fact that business professionals must wait until the very end of the project to review and provide input on the team's performance, and finalizing modifications at this point in the project is far more costly.

6. Build projects around motivated individuals. Give them the environment and support they need, and trust them to get the job done.

7. Working software is the primary measure of progress.It is better than progress reports for giving everyone the latest update on the project’s status, because it’s the most effective way for the team to communicate what they’ve accomplished. This is one reason why agile teams use iterative development. By delivering working software at the end of each iteration, and by doing a real product demonstration that shows everyone exactly what the team did, they keep everyone up to date on the progress of the software in a way that is almost impossible to misread.

8. Agile processes promote sustainable development. The sponsors, developers, and users should be able to maintain a constant pace indefinitely.

9. Continuous attention to technical excellence and good design enhances agility.

10. Simplicity—the art of maximizing the amount of work not done—is essential.Agile teams keep their solutions as simple as possible by avoiding building unnecessary features or overly complex software.

11. The best architectures, requirements, and designs emerge from self-organizing teams.Self-organizing teams share responsibility for all aspects of the project, from conceiving the product to project management to design and implementation.

12. At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behavior accordingly.By taking the time to look back and talk about lessons they learned after each iteration and also at the end of the project, agile teams constantly get better at building software.

POPULAR AGILE METHODOLOGIES

Just a brief definitions of them:
Scrum,extreme programing(XP), Lean and Kanban

1. Scrum and Self-organizing teams
Scrum is a potent framework that emphasizes incremental progress, continuous improvement, and cooperation in Agile project management. Scrum assists organizations in navigating the complexity and uncertainty of product development by emphasizing the delivery of value in small increments and cultivating a strong team dynamic.

2. Extreme programing(XP)
A strong Agile methodology, Extreme Programming places a strong emphasis on close client and developer cooperation as well as technical quality. Through the use of techniques like pair programming, TDD, and continuous integration, XP supports teams in producing high-caliber software that satisfies user needs in a setting that is changing quickly. With its emphasis on feedback, simplicity, and communication, it works especially well for projects whose requirements change often.

3. Lean
Within Agile, the Lean methodology emphasizes efficiency, continuous improvement, and customer satisfaction while delivering maximum value with little waste. Teams can improve their ability to collaborate, respond more quickly to changing needs, and streamline their operations by implementing Lean concepts and practices. This method works well with the Agile principles of flexibility and customer-focused development, which makes it a potent tactic in contemporary software development.

4. Kanban
Effective Agile methodology Kanban places a strong emphasis on efficiency, visual management, and ongoing development. Through the implementation of Kanban boards and concepts, teams may improve workflow management, foster collaboration, and increase customer value delivery. Because of its adaptability and emphasis on flow, it works especially effectively in settings where priorities and requirements shift regularly.

The figure above shows how Scrum, XP, and Lean all have the agile values at their core, and share some values, ideas, and practices with each other.

The Agile Software Development Life Cycle

The Agile SDLC is the structured series of stages that a product goes through as it moves from beginning to end. It contains six phases:
1. Concept: Define the project scope and priorities
2. Inception: Build the Agile team according to project requirements
3. Iteration: Create code factoring in customer feedback
4. Release: Test the code and troubleshoot any issues. When all of this is complete, the product’s final iteration can then be released into production.
5. Maintenance: Provide ongoing tech support to ensure the product remains serviceable
6. Retirement: The end of the product lifespan, which often coincides with the beginning of a new one. The product will enter this phase if it is being replaced with new software, or the system itself has become obsolete or incompatible with the organization over time.The software development team will first notify users that the software is being retired. If there is a replacement, the users will be migrated to the new system.

Depending on the project management approach a team chooses, the Agile life cycle will differ slightly. Scrum teams, for instance, operate in brief intervals called sprints, which are comparable to iterations. Additionally, they have distinctly defined roles—like Scrum master. Kanban teams, on the other hand, operate more like continuous flows without roles that are necessary. Extreme Programming is another example, where teams prioritize engineering techniques and work in shorter iterations. However, the goal of all software development teams is the same: to deliver working software to users on time.