802.11n is a wireless standard that is part of the IEEE 802.11 family of standards. 802.11n (wireless n router) is the latest in the family. 802.11 is the filing number used by the Institute of Electrical and Electronics Engineers (IEEE) to label Wi-Fi standards (also known as protocols). The Wi-FiAlliance is the industry body that agrees the standards and the IEEE ratifies them as official.  

802.11n builds on the previous 802.11g standard. The data transfer rate is significantly faster then 802.11g at up to 300 Mbit per second, as opposed to 54 Mbit per second. 802.11n is also know as wireless N. A wireless N router adheres to the 802.11n standard.

802.11n Wireless Router vs 802.11g

One of the main differences between 802.11n and 802.11g is the addition of MIMO (multiple-input multiple-output) technology. A wireless router with MIMO technology uses multiple antennas instead of just one. Some manufacturers are including MIMO technology in 802.11g wireless routers to increase the speed and coverage.

802.11n is backwards compatible with 802.11g and 802.11b standards. This means that devices built to a previous standard will still work with a 802.11n wireless n router.

Draft 802.11n and Pre-N

802.11n is still in draft stage and has not been fully ratified yet. As such, there may be some changes to the standard before it is ratified. It is expected to be ratifies in 2009. Despite this, most of the major wireless router manufacturers are releases draft n or pre-N wireless routers. The assumption being that the final published 802.11n standard will not be radically different from what it is today. So if you buy a wireless N router, you are actually buying a draft or pre-N router.