My programming skills have gotten a bit rusty because I haven't been coding for a long time now, due to the nature of my work (consultancy), but I recently had a nice idea for a web/mobile app and was looking at the various options I had in order to get back on track and try to develop it.

Is it correct to say that Flutter, and also React Native/other cross-platform framework and even Kotlin/Swift... they just take care of the front-end side of the app? I mean, if you can have BaaS solutions for your backend or utilize something like NodeJS, and then connect them somehow (I guess http calls?) to your flutter app, isn't it just that these frameworks essentialy handle the front-end or client-side of the app?