(plural: ‘advocates‘; pronunciation: the letter ‘c’ is said with a ‘k’ sound as in “king”)
a qualified person in law and justice who speaks in support (= in defence) or in favour of another person (his/her client) who is accused of some illegal activity by others or who accuses others of some illegal activity in a court of law [in this context, almost the same as a lawyer, barrister, solicitor and attorney];
a person who tells or tries to tell something good to others (nothing to do with law or justice);
(also ‘advocator‘) a person who supports a cause and tells others about the importance of that cause,
When he was accused of stealing his neighbour’s car, Mohammed approached an advocate and retained him to argue his case in the court of law.
My father was my best advocate; whenever I was in need of some advise, I would go to him. (nothing to do with law or a court of law, but just guidance on the matters that were too complicated for me to solve or understand on my own)
Nelson Mandela is an advocate of anti-apartheid in South Africa. (i.e. he thought apartheid was wrong and told everybody about it and fought the then government in support of banning apartheid)
Note 2: An ‘Advocate General’, on the other hand, is a very senior or experienced lawyer or law officer who is appointed by a government to oversee the law and justice department of the country or a certain region, and advise the judges of government courts.