An IP address (short for Internet Protocol address) is used to identify computers on the Internet. It works like a return address would on a piece of mail.
When your computer or device sends a request, like a search on Google, it tags the request with your IP address. That way Google knows where to send the response.
Your IP address will be a number, like 172.16.254.1 or 2001:db8:0:1234:0:567:8:1.