Everything on the Web could be accessed by using a string of digits called an IP (Internet Protocol) Address. This would be a pain in the ass.
Because human beings have trouble remembering long, random numbers, the Domain Name System (DNS), which replaces said numbers with easy-to-remember names, was created. Soyouwanttogetawebsite.com is a domain.
You access each page through its URL, which stands for Universal Resource Locator, or more commonly, web address. Connected web pages on the same domain form a website. “https://soyouwanttogetawebsite.com“ points to the home page of a site, “https://soyouwanttogetawebsite.com/how-websites-work” points to a different page on the same site, and “firstname.lastname@example.org” sends an email to an address connected to that site.
When you purchase a domain, you’re buying a spot in the DNS registry that sets you as the owner. That domain is yours as long as you keep paying the registration renewal fees. If you don’t pay, it reverts back to the public domain. So yes, you can lose your own domain if you forget to pay.
Owning a domain does not give you a website. You have to link a domain to a server for this, and for that, you’ll need a host.