The notarization of the document basically means that an official, usually called notary, approves that the document is signed by a certain person. The notary will identify the person signing the document and add a notary seal with notarial certificate to the document. That way any third party can rely on the fact that the signature of the document is real, not forged. This service is known as a notarized signature. But you must be aware of a risk that signing party can be unaware of the document’s content.
Although a notarization can make document completely legal and recognizable, the notarization can be insufficient to be recognized in other states. That happens, because every jurisdiction recognizes its own public power, and not that of other states. In cases, when a document must be notarized in order to be used in another jurisdiction - an Apostille Certificate can help and make document valid in foreign state.