When a domain expires, there's a period of a little over eight weeks when it is not active, but can still be renewed by the current owner. During this time period, the domain cannot be taken by anybody else, but if it's not renewed, it gets into the so-called Pending Deletion period which lasts five days. This is the time when ICANN-accredited registrar companies take backorders for this type of domains. When a particular name is backordered, the registrar will try to register it for the customer the moment it's deleted and available to the general public, which gives people the option to acquire a short and easy to remember domain that may have been used by somebody else up to now. In the event that the domain is quite appealing, several companies could 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 specific person will get that domain. Nonetheless, employing a backorder service will give you a better chance to get a particular domain than when you try to register it personally.
