There are two primary strategies for organizing your web space after you’ve registered and activated your domain: subdomains and subdirectories. For most purposes, the differences between the two boil down to aesthetics and usability.
Subdirectories function much like file folders on your computer. So emmadavidson.net might have a blog installed at emmadavidson.net/blog. As folders are nested, the resulting URL becomes more complicated. So if Emma is blogging for a class project, the URL could be something like emmadavidson.net/classes/wri101/projects/blog. The more complex the directory structure, the harder the URL will be to remember.
Subdomains are a way to create distinct areas of your web space with (relatively) simpler URLs. They also serve as an indications to users that they are in a new, different space. For example, Emma might build her Writing 101 blog in a subdomain for that class: wri101.emmadavidson.net/blog. Alternatively, she might group all her blogs in their own subdomain: blogs.emmadavidson.net/wri101. The content is still stored in nested files and folders, but using a subdomain keeps the URL shorter, and masks much of the complex directory structure from the browser.
You’re able to create as many subdomains as you like, and in each subdomain you can actually create a distinct, individual web site.
How To: Create Subdirectories and Subdomains