The purpose of a notary public is to give additional authenticity to documents that you need to sign. This doesn't apply to all types of documents, but typically those that are going to be extremely important to you. Here are a few examples of what documents require a notary public. 

Power of Attorney

A Power of Attorney legal document will grant the authority to someone on your behalf in a healthcare, financial, or legal matter. As you can imagine, those are very important situations where you want to ensure that the document giving that power is completely valid. That's where a notary public comes in since they will authenticate that you have given the power to the listed individuals, and you are doing so at a time when you are not under any coercion or duress. 

Last Will and Testament

Everyone should have some sort of estate planning in place, which outlines how a person's property and assets are distributed when they pass away. Since the document is often not read until after your death, a notary public will help ensure that the document is valid. Otherwise, it would be possible for someone to tamper with your last will and testament after you pass away, and then change it so that an unintended person is listed as an heir.

Real Estate and Loan Documents

There are many documents that need to be notarized during a real estate transaction. This includes mortgages, deeds, and loan documents. Since a real estate transaction is such a big purchase, with hundreds of thousands of dollars exchanging hands, it is crucial that the documents created are verified through a notary public. It will help protect you against future fraud, and ensure that everyone agrees to the terms outlined in the legal documents. 

Affidavits

Sometimes the document being verified is not related to property or decision making at all. Any time someone makes a written statement under oath, that statement is verified through a notary public. This is to ensure that the statement is done willingly and truthfully and that the statement is not altered after it is made. 

Having an affidavit signed by a notary public then allows the statement to be used as evidence in a courtroom. It will carry the same weight as if the person made the statement under oath while in the courtroom, and will be considered as evidence by a judge and jury.