A more thorough explanation:

JAG

JAG is short for Judge Advocate General. It is a branch of the United States Armed Forces that deals with military justice. The people who work in JAG are called judge advocates or judge advocates general.

When a soldier breaks a military law, they may be tried in a military court. The judge in that court is often a judge advocate from JAG.

If a soldier needs legal advice, they can go to a JAG office on their base and talk to a judge advocate.

These examples show how JAG is involved in military justice. They also show how JAG provides legal services to members of the military.