Sorry for the somewhat noob question, but how do you pick a library for making a GUI for your apps? My background is in physics, so most of my programming is perfectly find with a CLI that outputs a graph as a ps file or some csv. I am looking to learn about making some neat little GUIs. I was thinking it would be a good idea to try and build my GUI out of the browser so that my app can be as portable as possible, but does this mean it has to be in Javascript or can the backend be done in anything else?

I am not really sure what I am asking, but wanted to get a feel for how people approach front ends.

Thanks :)