A beta reader is usually a test reader of an unreleased work of literature or other writing (similar to beta testing in software), who gives feedback from the point of view of an average reader to the author. A beta reader is not a professional and can therefore provide advice and comments in the opinions of an average reader. This feedback is used by the writer to fix remaining issues with plot, pacing, and consistency. The beta reader also serves as a sounding board to see if the book has had the intended emotional impact.
"Beta reader" is an English term originally borrowed from the information technology/software industry where beta testers try to identify problems in a piece of computer software before its release.
Differences from other roles
A "proofreader" usually only looks at grammar and spelling and is a paid professional. A "critique partner" is a trained writer who "test reads" from the perspective of an author, unlike a beta reader who has little or no experience with writing. A beta reader can also serve as an "alpha reader" when reading a book draft that is still without an ending or is completely unrevised. Typically, a beta reader reviews a draft that has gone through at least one revision.