When a domain name expires, there's a time period of a little over eight weeks when it's inactive, but can still be renewed by its current user. During this time, the domain cannot be taken by anybody else, but if it isn't renewed, it enters the so-called Pending Deletion period that lasts 5 days. This is the time when ICANN-accredited registrar firms take backorders for these domains. If a particular name is backordered, the registrar will attempt to register it for the customer right after it's deleted and accessible to the public, which gives people a chance to get a short and easy to remember domain that may have been used by someone else until now. In the event that the domain is extremely attractive, several companies can try to register it in the same time and because this happens on a first-come, first-serve basis, there is no warranty that a particular person will get that domain. Nevertheless, employing a backorder service will give you a better chance to end up getting a specific domain than when you try to register it manually.