The domain
The domain is a name you lease, not a thing you buy outright. You register it with a registrar (GoDaddy, Namecheap, Cloudflare, Rebel, Hover and many others), pay yearly, and as long as you renew, it is yours. It also carries your email: info@yourbusiness.ca works because the domain's settings say where mail should go. Costs are in how much a domain name costs in Canada.
The hosting
Hosting is a computer, somewhere, that stores your website and sends it to anyone who asks for it. You rent space on it. Hosting comes in grades (shared, managed, cloud) that trade price for speed and support; see how much website hosting costs in Canada. If you use Shopify, Squarespace or Wix, hosting is included in the subscription.
How they connect
The domain's DNS settings (a small list of records kept at the registrar or at a DNS provider) tell the internet which server to send visitors to and where to deliver email. Change hosts and you update a record; the domain stays the same and visitors notice nothing. What DNS is explains the records.
Because they are separate, you can switch hosting companies without touching the domain, or switch registrars without moving the site. Bundling both with one company is convenient, but if that company is also your web developer, you have put the address, the files and the person who built them in one pair of hands. Keep at least the domain in your own account; the guide on owning and managing your domain explains how.