When it comes to skills and expertise, HR and management people classify you into one of these three categories:

1. I Person: Focused on just one skill (such as JavaScript, PHP, Node, CSS, Photoshop, HTML, etc.) to an expert level (the letter "I" indicates the depth of specialization in one field).
2. T Person: Focused on one skill but still covers an entire broader area (such as backend programming, frontend design, database administration, micro-services, etc). The I part represents the focus, and the dash above represents the breadth or range.
3. X Person: Has established enough reputation in a particular skill or skill range that s/he can guide other people and manage them. People like Guido, Linus, Rasmus, etc. might fall in this category.

So, what kind of person are you?

Edit

Though not officially acknowledged, there is also an M Person - the generalist who "specializes" in too many things such as the GP/MBBS Doctor or a Full Stack Developer.