什么是C＃迭代器和生成器，以及如何使用它们

I am a VB.Net developer, kind of newbie in C#, While looking in C# documentation I came through Iterators and Generators, could not fully understand the use, I there anyone who can explain (in vb perceptive; if possible)I am a VB.Net developer, kind of newbie in C#,