system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is .NET Framework for?
gpt
It's a bunch of code that people who write programs can use to make it really easy to do a bunch of general stuff.

For example.  Instead of writing out all sorts of code to read stuff from a file you can say:

    string[] AllLines = File.ReadAllLines(@"C:\Folder\file.txt");

And that opens that file, reads all of the lines, and shoves it into a variable (like a storage box for information) called AllLines.  You can then use that to do stuff for the user.

Microsoft wrote the code for ReadAllLines() so you don't have to.  It's called a "method", and it's just a chunk of code that does something.  ReadAllLines() It's part of a something called a "class" named "File" which is part of something called a "namespace" called system.IO (I think) and that's part of the .Net Framework.  All of that (and a ridiculous amount more) is made by microsoft.