Beta Readers

In a number of discussions I have seen people refer to beta readers. The concept introduces a few questions into my mind; specifically I was wondering at what point a beta reader usually reads a story, what is the result of a beta read, and how is it different than an editor.

I am asking, because I am not feeling particularly confident about either of the two stories that I am working on and was wondering if finding a beta reader and then an editor at a later point would be a wise approach before submitting. If so, is there anybody that would be interest in either being a beta reader or an editor for me? If curious, I can provide you with a message giving you a bit more of an outline on the first of the stories.