What are the uses of “using” in C#?

Question

User kokos answered the wonderful Hidden Features of C# question by mentioning the using keyword. Can you elaborate on that? What are the uses of

Answer 1

using can be used to call IDisposable. It can also be used to alias types.

using (SqlConnection cnn = new SqlConnection()) { /*code*/}
using f1 = System.Windows.Forms.Form;