What is localhost? It’s a name and address, usually used by a web browser to find a web server on your computer. Instead of typing myfavoritewebsite.com you type localhost in the URL bar of your web browser. If your computer has a web server, and is configured properly, you will see a basic web page. On Grendel, my ancient iMac, calling up localhost in my browser displays a message, “It works! And unlock!” No idea the last bit — what unlocked?

Localhost like any self-respecting website address also has a unique IP address: typing 127.0.0.1 in the URL bar of your web browser displays the same results as typing in localhost. What’s an IP address? IP stands for internet protocol which refers to a set of standards (protocols) used to communicate on the internet. Imagine if every computer on the internet spoke a different language. Because computers transfer data with the same standards, data moves quickly and efficiently. Your web pages and email show up as you (hope and) expect.

The difference between localhost and any URL like myfavoritewebsite.com is localhost traffic never travels on a network. Data is transmitted within your computer. People typically use localhost to do web-based software development on their computer then transfer files to a remote web server for test and launch.