What does it mean to "register" a domain name?

When you register a domain name, you are inserting an entry into a directory of all the domain names and their corresponding computers on the Internet.  This allows you to point (or forward)  this domain name to your web site, and use it for email.

Domain names are registered for a specific period of time (usually in increments of one year) and must be renewed at the end of each registration period.  You own the domain for the life of the registration only.

If you allow the domain to expire, it will no longer be active and you will not own the domain.  If you do not renew the domain in time, the domain eventually becomes available to others to register.

Each registry has different rules for how long a domain may (or may not) be held during a grace period, allowing time for the previous registrant to renew the name.
 
You do not lose any time when you renew a domain early.  We highly suggest you keep track of your domain expiration dates, and renew well in advance of expiration to avoid unintentional down time or loss of the name.