An autoencoder is like a special kind of computer program. It "looks" at a thing (like a picture, or an audio clip, or a word) and it tries to figure out how best to describe that thing using only a few numbers. For example, if you have a picture of a cat, the autoencoder might try to figure out how to represent that picture using only 4 numbers. These 4 numbers can be thought of as a kind of "shortcut" that can help a computer understand things. Autoencoders are useful because they can help computers understand things more quickly and accurately.