The following is an excerpt from this
To grossly oversimplify, it's a package of common support software that can be used by programs so that they don't all have to re-write the same software over and over again. More specifically, it's aimed at users of Microsoft's newer versions of programming languages like C#, Visual Basic .NET and others. The .NET framework provides a broad array of functionality that can be used by programs written in those languages to perform common tasks, most commonly things that involve interacting with Windows itself.
So you may well have programs installed on your machine that rely on the .NET framework, and thus deleting .NET will cause that program to fail. Over time, more and more programs have come to rely on .NET, so chances are actually pretty high that you have at least one and perhaps more that rely on .NET.
Microsoft has this
article on the benefits of Net. Framework.