802.11b: Known as Wi-Fi, 802.11b is currently the leading market standard for wireless local-area networking. This version transfers data at 11 Mbits/s at distances of up to 300 ft. It operates at 2.4 GHz, so it shares spectrum with cordless phones, Bluetooth products, and many other unlicensed devices. It uses the complementary-code-keying (CCK) modulation scheme.
802.11a: Also known as Wi-Fi, 802.11a has yet to be widely accepted in the industry. It operates in the 5-GHz range at a 54-Mbit/s data rate and uses orthogonal-frequency-division-multiplexing (OFDM) modulation, which is a faster data-transmission scheme than CCK. But it's not backward-compatible with 802.11b.
802.11g: Like 802.11b, this version uses OFDM. It runs at 2.4 GHz and is expected to operate at 54 Mbits/s when it becomes an official standard, which the IEEE expects by July. It is backward-compatible with 802.11b. The "g" standard is still in the draft stage, but judging by the products that appeared at the recent International Consumer Electronics Show, "g" will likely be the standard of choice for most wireless network manufacturers.
Some vendors are covering their bets by using chips that combine 802.11a, b, and g for 54-Mbit/s data rates over the 2.4- and 5.2-GHz bands. At least one company has announced a combination Wi-Fi/Bluetooth chip. Motorola, Nokia, and Samsung, among other manufacturers, plan to integrate Wi-Fi into their cell phones.