802.11 (with no letter suffix) was the original standard in this family, ratified in 1997. 802.11 defined WLANs that operate at 1-2 Mbps. This standard is obsolete today.
Each extension to the original 802.11 appends a unique letter to the end of the name. While 802.11g and 802.11n are the most interesting to the average consumer, many other extensions exist or are under development.
See also: IEEE 802.11 Working Group Standards