The broad field of building computer systems that perform tasks normally requiring human intelligence.
Friendly Description: Artificial Intelligence is the big umbrella name for all the ways we teach computers to do things that usually need a person's brain, like recognizing a face, understanding a sentence, or suggesting a song you might like. It's not magic, and it's not a robot from a movie. It's more like a very patient student that learns from lots and lots of examples and then helps us with everyday tasks.
Example: When your phone unlocks by looking at your face, that's AI. When a streaming service suggests a movie you'll probably love, that's AI. When your email filters out spam before you ever see it, that's AI quietly working in the background to make life a little smoother.