This summary is not the rule. The rule text controls.
Sometimes a lawsuit includes several parties, but not everyone has a claim against everyone else. If one person in the case has nothing to do with another person's dispute, being lumped into the same case can waste their time and money or cause unfair problems for them.
To fix this, the judge can step in and issue orders to protect that person. This might mean holding separate trials for different parts of the case, or making other decisions to keep things fair and moving efficiently.
The main goal is to stop anyone from being unfairly dragged into a fight that is not really theirs. If a party is not making a claim against someone else, and that other person is not making a claim against them, the court can separate their issues so no one gets stuck with extra costs, delays, or headaches that don't belong to them.