Schrodinger's cat is a thought experiment and a paradox.
It was used to emphasize nonsensical physics theories that are impossible.
Simply put it places a cat in a sealed container with poison, a geiger counter, radioactive material, and a hammer.
The amount of radioactive material must be so small enough that it only had a fifty-fifty chance of being detected over the course of an hour. If the geiger counter detected radiation, the hammer would smash the poison and kill the cat. Until someone opens the container and observed the system, it was impossible to predict if the cat would live or die.
This means the cat is both alive and dead at the same time. This is the paradox. Nothing can be dead and alive.
This experiment was used to project the implication of an interpretation of quantum mechanics.