Authentication is the process of proving that someone or something is really who or what they claim to be. When you log into your email account by entering your password, you're authenticating yourself: you're proving to the computer that you're really you and not someone else trying to break into your account.

Think of authentication like showing your library card to check out books. The librarian needs to verify that you're the actual owner of that card before letting you borrow anything. Similarly, websites and apps use authentication to make sure the person trying to access an account is the real owner.

Authentication can take many forms. Sometimes it's a password you memorize. Other times it might be a fingerprint scan on a phone, a code sent to your email, or even your face recognized by a camera. Banks often use multiple forms of authentication for extra security: they might ask for your password and send a code to your phone.

The word comes from the same root as authentic, which means genuine or real. When you authenticate something, you're establishing that it's authentic. Museums authenticate paintings to prove they're real and not forgeries. Scientists authenticate fossils to confirm they're actual prehistoric remains and not modern fakes.