I dont understand what .NET is. I understand that its a framework but what languages are used within it etc?
It’s a set of libraries that comprise a framework for building applications for Windows (and with .Net Core, all other platforms as well). Just lots and lots of utilities you can use for building software.
It runs on a virtual machine called the Common Language Runtime. There are multiple languages that run on top of that (the MS ones like C#, F# and Visual Basic, as well as CLR-specific implementations of other languages like Python).
If you’re not sure of what a VM is: it’s an environment that code can execute inside, so you install the VM, and that in turn lets you run code in certain languages. As another example: the Java VM, which can run (for example) Java, Scala, Clojure, Kotlin, Python, Ruby amongst multiple others. It makes the code portable: someone just installs the VM and then they can run your code.