A domain is your site’s address (e.g. yourcompany.com). You register it with a registrar, usually for a year with renewal. Check if the price includes WHOIS privacy and whether there are hidden fees on renewal.
Hosting is the server space where your site files live. For WordPress or PrestaShop you need hosting with PHP and a database. Look at bandwidth, disk space, backups, support and whether SSL (HTTPS) is included.
Shared hosting is often enough for small sites. Larger shops or high-traffic sites may need a VPS or dedicated server. If unsure, ask your developer what hosting they recommend for your chosen technology.