People talk about "the website" as if it were a single object. It is really three separate things, and each can belong to a different person.
1. The domain
The domain is your address on the internet, for example yourbusiness.com. You rent it from a registrar, usually for a yearly fee. If you lose it, customers can no longer find you, and email addresses that end in that domain stop working too.
2. The hosting
Hosting is the computer (a server) where your website's files live and from which they are sent to visitors, day and night. It is also paid for regularly, monthly or yearly.
3. The website itself
This is the pages, design, text, images and database, plus the admin area where you change things. Developers call the files that make it work the code.
Why this matters
If a developer registers the domain in their own name, holds the only hosting login, or keeps the files, you depend on them for your own business. Later, you may find you cannot move, fix or even renew the site.
Rule of thumb: the domain should be registered in your name with your email, you should know where the site is hosted and what it costs, and you should have the admin login and a copy of the files.
Your task
Write down, for your own website (or the one you plan): who owns the domain, who pays for hosting, and who has the admin login. If you cannot answer one of these, that is your first action.