The simple version of machine learning is this: we give a machine a lot of data regarding a topic. Let's say images of cats.

After showing it hundreds, or even thousands of cats, we then give it a test. For example, asking it to name the animal in this picture.

We know we've succeeded when the machine can recognize a concept on a regular basis.

And of course, machines might not get it right at first. But we'll keep showing them images of cats and testing them until they do.