When you buy a domain name, you register it to yourself (or your company) on a yearly basis. Every year you renew ownership of your domain name(s). Renewal costs anywhere from $5 to $15 depending on your domain name registrar.
You are usually given the option for a multi-year renewal which will save a few dollars and headaches. Multi-year renewals are a good idea if you have a domain name you know you will want for the foreseeable future.
An expired domain is simply a domain which becomes available for purchase by someone else because the previous owner failed to pay the yearly renewal fee.
Who would someone let a good domain name expire?
- Absentminded website owners who simply neglected to renew their domain names
- Webmasters who got tied up in other ventures or interests
- Webmasters who discontinued a site due to time constraints
- Webmasters who ran out of money to continue to operate

Your domain name registrar should send you several renewal notices so you don’t miss renewing a domain name you want. Make sure you have a working email address on file so you don’t miss a renewal notice!
These days, when a domain name expires, your registrar may “take over” the name for a period of a few months. If you decide you do want the name after it’s expired and the registrar has assumed control of it, your registrar will charge anywhere from $50 to $150 (those are the prices I’ve seen) to pull that domain name out of limbo and reinstate it to you… I waited six months to get a domain name back once to avoid the fee! (I wanted it for sentimental reasons.)
So don’t miss your renewal if there is any chance you can use that domain name!