In Schrodinger's thought experiment he imagined a cat in a closed box with a deadly poison. The poison would be released if some radioactive atoms decayed. This decay occurs naturally when a physically unstable form of an element (such as uranium) sheds energy and subatomic particles. The math of quantum mechanics can calculate the odds that the material has decayed — and in this case, released the poison. But it cannot identify, for certain, when that will happen.
So from the quantum perspective, the cat can be assumed to be both dead — and still alive — at the same time. Scientists called this dual state a superposition. And the cat remains in limbo until the box is opened. Only then will we learn if it’s a purring kitty or a lifeless corpse.