A more thorough explanation:

A judge advocate is a legal officer in the Judge Advocate General (JAG) Corps who represents the Army in military legal matters. They provide legal advice to help uphold military law, as specified in the Uniform Code of Military Justice. Judge advocates play a key role in referring cases to courts martial, negotiating pre-trial agreements, and taking actions on cases after court martial has concluded.

For example, before a convening authority refers charges to a general court martial, the authority’s staff judge advocate is responsible for giving written advice and recommendation on the given charges. A convening authority must also seek a judge advocate’s advice before referring charges to a special court martial.

All judge advocates must graduate from an ABA-accredited law school and be certified to practice law. Although most judge advocates do not need prior military experience, entering the JAG Corps requires completion of a multi-phase orientation and a professional development course.

There are more than 1,000 judge advocates on active duty and nearly 4,000 in the U.S. Army Reserve and the National Guard.