From the August 2016 newsletter
“Beta Reader” means someone who evaluates a manuscript – a term probably adapted from the software industry, where programmers release a "beta" version of a new program to people who will test it.
Beta readers are not editors but are volunteers who can give you feedback about your book. Best friends, significant others and family members aren’t likely to be the best beta readers – they’re predisposed to loving whatever you write.
Beta readers are not the same as a read-and-critique group. A beta reader will read your entire manuscript, on their own, and develop a personal response to it. Some online writers suggest arranging three+ beta readers, individuals who are honest, give constructive comments, and have the time.
Give them the very best writing you can produce on your own, not your first draft. Let your beta reader know what questions you would like answered. Do you want comments on the strength of the characters, the organization of the concept, the flow or pace of the action, or on areas where they felt something was missing? Ask them to note their thoughts as they read. Provide them with the book in the format they would prefer, digital or paper.
When you receive a beta reader’s comments ask yourself, “Will addressing this comment make for a better book?” If so, take their advice and apply it to your next revision. If not, thank them: don’t defend yourself. You don’t have to accept every piece of advice you get.
If you would like names of possible beta readers from SDWE/G or you’re available as a beta reader, contact Sandra Yeaman at firstname.lastname@example.org.
Source: results of a Google search.