These two terms get mixed up all the time, but they're actually two separate things that work together.
A domain name (like yourbusiness.co.za) is your address on the internet. It's what people type into their browser to find you. You register (rent) it for a year or more at a time.
Web hosting is the actual storage space where your website's files, images and emails live. Think of the domain as your street address, and hosting as the house itself.
You need both: a domain without hosting has nowhere to point to, and hosting without a domain has no address for people to find it. Most South African businesses buy both from the same provider for convenience, but they don't have to come from the same place.