A domain is a unique address that directs internet users to a website. It's a crucial element for any online presence as it gives your website a professional and memorable address. There are several places where you can buy a domain.

Domain registrars: These are companies that specialize in registering and selling domain names. Some popular domain registrars include GoDaddy, Namecheap, and Network Solutions. These companies allow you to search for and purchase available domain names, and also offer additional services such as domain privacy and hosting.

Wix and Shopify, also offer the option to purchase a domain name through their platform. This can make it easier to manage your website and domain in one place.
When purchasing a domain, it's important to consider the price, renewal fees, and any additional services that may be offered.