Domains are registered on an annual basis and you can have one registered for up to 10 years at a time. Once you have a domain registered, you have to renew the registration on an annual basis (or before its expiration date if you've registered it for longer than 1 year).
Everyone has to renew their domain name in this same way (even the multi-million dollar companies out there). If you don't keep the registration of your domain name up to date you can, unfortunately, lose possession of your domain.
Due to this, in a sense, no one can ever outright own their domain name without having to keep the registration for their domain active.