While many fields in science depend on hard facts and numbers, there are some parts of science where it's not quite so black and white. Schrödinger's cat is one such part of physics. Quantum physicist Erwin Schrödinger postulated that some forms of matter can exist in more than one state at the same time. He used the example of a cat, in a closed box with radioactive material, enough to be lethal. Until the box is opened and the cat is examined, no one knows if it's alive or dead. So, theoretically, the cat is both alive and dead, existing in more than one state of matter at the same time. It's called a "thought experiment" and it challenges students to understand scientific theory and the fact that until something is proven, no theory can be said to be right or wrong, and allegorically, the cat cannot be assumed dead or alive.
There are essentially two fields of physics. Classic physics which explains most physical laws like the how fast an object falls or how strong the pull of gravity is. Then there is quantum physics which seeks to explain those phenomena that classic physics cannot fully prove. Quantum physicists deal in theory, since it's not always possible to see what goes on at the particle level of atoms in matter. Often quantum physicists have to look at the mechanics of how something works to theorize what state it might be in. Whether classic or quantum, physicists have been been debating the life or death of this famous cat for centuries.