A backorder is used to attempt to register a domain that has already expired and is about to be released to the general public. A backorder can be submitted for any domain, but only domains in our Pending Delete Domains list will be attempted. You can find the Pending Delete Domains List on the Auctions page
The user who places the backorder first automatically gets the starting bid when a backorder auction starts. If no one else who placed a backorder on the domain has bid yet, it will look like you are the only person who placed a backorder.
Backorder Auctions are listed as "Pending Delete" on Sav's Auctions page.
You can learn more about backorders here.