A notary is someone with the legal power to witness signatures, verify documents, and take depositions.
A notary — also known as a notary public — is a person who has been licensed by a state to perform a few legal functions. The most common one is to witness signatures. For many types of paperwork, you need a notary to be present as you sign, which makes the paperwork official. Notaries also have the power to verify various types of documents and are allowed to take depositions (statements) in some legal situations.