In order for your Mac to connect to the Internet, it must have a unique number assigned to it called an Internet Protocol (or IP) address. The IP address of your computer can be thought of as its mailing address. Without it, messages can’t be sent or received.
You might find you need to look that number up, such as when you’re trying to fix a network access problem. We could write a very large book describing all the ins and outs of the Internet protocol, but for this how-to, we’ll just show you a few quick and easy ways to find out what the IP address for your Mac happens to be.