ELI5: Explain Like I'm 5

Invariant differential operator

An invariant differential operator is a type of mathematical tool that is used to help solve mathematical equations. It works by applying a specific set of rules to an equation which helps simplify it. If the equation is too complicated, using an invariant differential operator can help break it down into simpler parts that are easier to solve. Think of it like a chef using a cutting board to chop up onions to make them easier to cook.