When you register your domain with a registrar most of the time the company you go through will offer to host your website for an added cost. Furthermore, when you go through any hosting company what you are signing up for is a managed hosting service. What this means is that the company you have gone through is managing all of the different things required to get your website up and running and to keep it that way. The hardware, software, upgrades, backups are all part of the services you pay for.