A quick definition of model jury charge:

A model jury charge is a set of instructions that a judge gives to a jury about the law of a case. It helps the jury understand what they need to consider when making a decision. Sometimes, the jury may have questions or need more information, and the judge can give them additional instructions. There are different types of instructions, such as mandatory instructions that require the jury to find for one party, and cautionary instructions that tell the jury to disregard certain evidence. Model jury instructions are usually approved by a state bar association and are considered authoritative by courts.