In c# what does 'where T : class' mean?

Question

In C# what does where T : class mean?

Ie.

public IList DoThis() where T : class

Answer 1

it means that the type used as T when the generic method is used must be a class - i.e. it cannot be a struct or built in number like int or double

// Valid:
var myStringList = DoThis();
// Invalid - compile error
var myIntList = DoThis();