A domain is the address people type to reach you, such as example.com. Web hosting is the server space that holds your website, databases, and any mailboxes included with the plan.
They are separate services. A domain can be registered without hosting, and a hosting plan can use a domain registered elsewhere. For a website to work, the domain's DNS must point to the hosting service and both services must remain active.
Cancelling hosting does not normally cancel a separately registered domain. Check both services in the client area before changing or cancelling either one.