I have a dumb question: What is "Windows Build Support (IL2CPP)"?

I'm self taught with Unity and Blender and for a good while now I have been using an older version of Unity (Unity 5.3.5f1) and decided to upgrade to a newer version because of some issues I noticed with importing models. I'm about to install but I noticed this new option for Windows Build Support (IL2CPP) and never having heard it before I tried Googling it but there's no clear/specific answer. I read something about compiling C# to C++ (I think) and I really want to make sure I'm not skipping out on anything vital.

I'm working on my first game ever and my aim to for it to work on most Windows computers and I don't know if this is a vital component or if I can go back and download it if it turns out I actually need it.

 

Nevermind, I found it here but I'll put a link to the answer here just in case anyone else is stuck with this:
https://docs.unity3d.com/Manual/IL2CPP.html

 

And yes, you can always re-run the installer to install any component you need later.

 

For anyone who wants the TLDR; version, a "normal" build using the mono runtime compiles to IL, which when you run your build is compiled on the fly to machine code. IL2CPP goes further by compiling the IL to C++ and then to machine code during the creation the build.

 

Other platforms support AOT and IL2CPP, but don’t allow JIT compilation- which the scripting link doesn't explain (it lists AOT and IL2CPP)- which platforms don't allow JIT?