WLAN

WLAN (Wireless LAN) also called Wifi.

802.11b
This was the first standard in the 2.4 Ghz spectrum. It featured 13 channels in Europe (11 in the USA and Canada). And had speeds up to 11 Mbit/s.

802.11g
Again in the 2.4 Ghz frequency this achieved bandwidths up to 54 Mbit/s. The bandwidth used required a footprint of 3 channels so it's logical to use 1, 6 and 11 so that no overlapping occurs.

802.11n
Achieved speds up to 150 Mbit/s and with bonding 300 Mbit/s. This would ultimately take up 6 channels in the 2.4 Ghz spectrum. Also available in this is 5 Ghz spectrum.

802.11ac
Near gigabit speeds, very new in 2013.