An advocate (AD-və-kit) is someone who supports a cause, like an advocate for outdoor recess. Advocate (AD-və-kate) is also a verb meaning to speak in favor of, so you can advocate for that outdoor recess by urging your school to play outside!
The Brits and Canadians prefer to say barrister instead of "lawyer," but they mean the same thing. A barrister is a person who goes to court on behalf of the defense or the prosecution.
An attorney is a lawyer. Attorneys sue people, defend people, and serve as experts on the law.
When there's any kind of legal issue, attorneys will be involved. They're the legal experts with law degrees who are also known as "lawyers." You'll often find them in court, defending clients or trying to put criminals in jail. Attorneys work for businesses, schools, the government, and individuals. So if you get arrested, need to write a will, or have to hash out a binding contract, an attorney is the person to call.