A beta reader (also spelled betareader, or shortened to beta) is a person who reads a written work, generally fiction, with what has 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." Generally, beta readers do some or all of the following:

• Check for spelling, punctiation and grammatical errors
• Help with characterization
• Fact checking
• Help with sentence structure and flow
• Check for plot holes, problems with continuity, characterization and believability of situations within the story
• Other critiquing

Find A Beta
Beta Search | Fandom Betas

Helpful Places
Little Details | Fandom Grammar | Finishing WIPs

Keep It Ethical
Stop Plagiarism | Art Theft

And remember -- if you feel like you don't need a beta, that's perfectly okay! A lot of writers do not use them. However, it is always a good idea to run spelling and grammar check in your word processor, then proofread it yourself and, if you want to and have a friend available, have someone read through for a quick proofread as well. Even the best writers can make the occasional mistake and miss it.