A plea colloquy refers to the statements and advisement that a judge gives to a person who is about to plead guilty.
The purpose of a plea colloquy is to make sure that the person knows exactly what they are about to do. This means making sure that they understand all of the legal implications of pleading guilty.
Plea colloquies generally take place in open court. During the plea colloquy, the judge will also try to validate that the defendant is making the plea voluntarily, and that the person's plea is based on the facts of the case and not on something else.
Ultimately, a defendant will have to make the plea decision themselves. However, by making a plea colloquy, judges attempt to make sure that defendants have all of the information they need to make this decision.