It was several years after I wrote my first novel before that I found out about the revered Beta Reader. I’d heard that phrase being thrown around five years ago at my first writer’s conference, and not wanting to seem as ignorant as I really was, I nodded my head and grinned when the conversation came too close to me to reply intelligently. According to WikipediA, “a beta reader is a person who reads a written work with what as been described as a critical eye, with the aim of improving grammar, spelling, characterization, and general style of a story prior to its release to the general public.”
If you're a writer and you don't have a couple of beta readers in your contact list--get them! They do not need to be authors, although that would be a plus. But they do need to be avid readers and know what makes a good story.