802.11b - describes somewhat faster data transfer rates and a more restrictive scope of transmission technologies. This standard is also widely promoted as Wi-Fi by the Wireless Ethernet Compatibility Alliance(WECA). 1, 2, 5.5 or 11 Mbps.
802.11a - describes much faster data transfer rate than (but lack backwards compatibility with) 802.11b. 6, 9, 12, 18, 24, 36, 48 and 54 Mbps.
802.11g - the most recent draft based on the 802.11 standard that describes data transfer rates equally as fast as 802.11a, and boasts the backward compatibility to 802.11b.
802.11a - describes much faster data transfer rate than (but lack backwards compatibility with) 802.11b. 6, 9, 12, 18, 24, 36, 48 and 54 Mbps.
802.11g - the most recent draft based on the 802.11 standard that describes data transfer rates equally as fast as 802.11a, and boasts the backward compatibility to 802.11b.