What is "beta reader"

n. A person proofreading another person's text before the latter makes it available to the general public.

An alpha reader or beta reader (also spelled alphareader / betareader, or shortened to alpha / beta), also pre-reader or critiquer, is a non-professional reader who reads a written work, generally fiction, with the intent of looking over the material to find and improve elements such as grammar and spelling, as well as suggestions to improve the story, its characters, or its setting. Beta reading is typically done before the story is released for public consumption. Beta readers are not explicitly proofreaders or editors, but can serve in that context.

Elements highlighted by beta readers encompass things such as plot holes, problems with continuity, characterisation or believability; in fiction and non-fiction, the beta might also assist the author with fact-checking.