When you register domain in a normal way, you are assigned to be the domain administrator and entered into WHOIS. For the year lease, the domain name is yours, and your registrar cannot take it down unless they have the legal reason to. You can also transfer your domain to another registrar.
Proxy registrars like Njalla keep ownership of the domain, keep themselves in WHOIS and can take your domain back for any reason at any point, because it's actually theirs. You also cannot move it to other registrars for the same reason.