A dense plasma focus is a machine that creates a super hot, super bright ball of gas called plasma. Imagine playing with a balloon and squeezing it so hard that it pops and releases all its air. That's kind of what the dense plasma focus machine does, but instead of air, it squeezes gas atoms so hard that they turn into plasma.
To do this, the machine uses a big metal chamber filled with gas. Inside the chamber, there are two electrodes, which are like little metal sticks. One electrode is at the bottom and the other is at the top. When the machine is turned on, it sends an electric jolt through the gas, which creates a magnetic field that pulls the gas towards the center of the chamber.
As the gas gets closer to the center, it speeds up and gets hotter and hotter until it turns into plasma. This plasma ball is so hot and bright that it can be used for all kinds of things, like studying nuclear fusion, which is a way of producing clean energy by imitating what happens in the sun.
So to sum it up, the dense plasma focus is a machine that squishes gas atoms so hard that they turn into a super hot and bright ball of plasma that scientists can use for lots of cool experiments.