This summary is not the rule. The rule text controls.
A judge is not allowed to have private conversations about a case with only one side. This means that if you have a case in front of a judge, you cannot talk to the judge about the facts or the law of your case unless the other side is there too, or unless the court rules specifically allow it as part of the normal court process.
This rule exists to keep things fair. Both sides deserve to know what the judge is hearing and to have a chance to respond. If someone tries to talk to the judge alone about their case, or tries to pressure or influence the judge outside of the proper court process, the judge must refuse to allow it.
The judge also cannot let anyone influence a decision in ways that break the state's rules for judges. This protects everyone's right to a fair hearing where both sides are treated equally and the judge makes decisions based only on what happens properly in court.