Okay kiddo, a penning trap is a special kind of device that scientists use to trap tiny particles, like atoms. It's kind of like a little cage that holds the particle still so the scientists can study it.
The trap works by using a magnetic field and an electric field. Think of the magnetic field like a big magnet that pulls the particle to the center of the trap and the electric field like a force field that stops the particle from escaping.
Scientists use the penning trap to study the particle's properties, like its mass and charge. They do this by measuring how the particle moves and reacts to the magnetic and electric fields.
So basically, a penning trap is a scientist's tool for catching and studying really small things like atoms!