Automatic number identification is a fancy way of saying that when someone calls you, a computer can tell you who is calling before you even pick up the phone. It's like having a magical machine that knows who's on the other end of the line!
The computer does this by looking at the phone number of the person calling you. Every phone number is unique, kind of like a name or a fingerprint. When someone calls you, their phone number shows up on your phone. The computer can see that phone number and then check it against a database of phone numbers that it has.
Once the computer finds a match, it can tell you who is calling you. This can come in handy because sometimes people can call you from numbers you don't recognize, or you may not have a number saved in your phone for someone. With automatic number identification, you can know who is calling without having to guess or answer the phone blindly.