What It Is
A subdomain is a prefix added to the front of your domain name, separated by a dot. In book.smithsalon.com, the word book is the subdomain. If your domain is a building, a subdomain is like a separate suite inside it with its own door. The familiar www in front of many addresses is technically a subdomain too.
Why It Matters for Your Business
Subdomains let you run different tools under one brand without buying new domains. A salon might keep its main site at smithsalon.com, its online booking at book.smithsalon.com, and a customer portal at clients.smithsalon.com. Each one can live on a different service, yet customers still see a single, consistent address.
Good to Know
Search engines can treat a subdomain somewhat like a separate site. If you want a blog to help your main site rank, many people prefer a folder like smithsalon.com/blog over blog.smithsalon.com. Subdomains are usually free to create in your DNS settings. Your host or DNS provider can add them in a few minutes.