IEEE 802.11

802.11 refers to a family of specifications developed by the IEEE for Wireless LANs. The original 802.11 specification, approved in 1997, was intended for short range low speed device communication. It featured FHSS and DSSS frequency modulation, with a maximum data rate of 1 to 2Mbps, depending on modulation. The 802.11 workgroup has the option for two different type of network setups: ad-hoc and infrastructure.

In ad-hoc mode, devices connect to each other 'on the fly', with no order. Although all of the devices in range assign one machine to be the master and the rest to be the slaves. ad-hoc is convenient, but inefficient, all devices can communicate with each other instead of one central point.

This is where infrastructure comes in. All of the devices associate themselves with a central point, called the Access Point or AP. Each device waits it's turn, with the AP polling them (usually), as such each device communicates with only the Access Point. The Access Point will relay information to other devices as necessary.

This setup is extremely efficient, ensuring a maximum latency between the devices and the access point. However, It didn't take long before 2Mbps wasn't enough, and in 1999, The IEEE made a ratification to 802.11 called IEEE 802.11b, and thus the task groups within 802.11 were born.

It's important to point out that on almost all wireless products, there's an advertised rate of throughput. On many consumer brands, they advertise 11Mbps or 54Mbps. This is not the actual throughput that you'll notice. In wireless networking, there's a surprising ammount of overhead for the transmission. Similar to TCP connections. At a radio rate of 11Mbps, you'll see approximately 7Mbps of data rate on a "good day".
Thanks to spiregrain for reminding me of this important fact.

A current list of all 802.11 task groups:

• IEEE 802.11 (1997) Legacy - Original Standard (2.4Ghz, 2Mbps)
• IEEE 802.11a (1999) 5.2, 5.3, & 5.8Ghz standard (54Mbps)
• IEEE 802.11b (1999) Enhanchment of Legacy, 2.4Ghz, 5.5Mbps and 11Mbps additional
• IEEE 802.11d (2001) New Countries
• IEEE 802.11e (2002) Improvements: QoS and packet bursting
• IEEE 802.11f (2003) Inter-Access Point Protocol or IAPP
• IEEE 802.11g (2003) Improvement on 802.11b, 54Mbps.
• IEEE 802.11h (200?) Extensions for European countries in the 5Ghz spectrum
• IEEE 802.11i (N/A) Enhanced Security over 802.11e (In Development?)
• IEEE 802.11j (N/A) Extensions for Japan (In Development?)
• IEEE 802.11n (Dev) Provisions for 100Mbps or faster data rates. In Development.

Sources:
http://en.wikipedia.org/wiki/IEEE_802.11
http://www.wi-fiplanet.com/news/article.php/925091
http://grouper.ieee.org/groups/802/11/Reports/tgd_update.htm