802.11ac (also called 5G Wi-Fi) is the fifth generation of Wi-Fi technology, standardized by the IEEE. It is an evolution of the previous standard, 802.11n, that provides greater bandwidth and more simultaneous spatial streams. This allows 802.11ac devices to support data transfer rates that are several times faster than those of 802.11n devices.
Unlike previous Wi-Fi standards, which operated at a 2.4 GHz frequency, 802.11ac operates exclusively on a 5 GHz frequency band. This prevents interference with common 2.4 GHz devices, such as cordless phones, baby monitors, and older wireless routers. Computers and mobile devices that support 802.11ac will benefit from the 5 GHz bandwidth, but older wireless devices can still communicate with with an 802.11ac router at a slower speed.
The initial draft of the 802.11ac standard was approved in 2012, but 802.11ac hardware was not released until 2013. The initial 802.11ac standard (wave 1) supports a maximum data transfer rate of 1300 Mbps, or 1.3 Gbps, using 3 spatial streams. This is significantly faster than 802.11n's maximum speed of 450 Mbps. It also means 802.11ac is the first Wi-Fi standard that has the potential to be faster than Gigabit Ethernet. The second 802.11ac standard (wave 2) will support twice the bandwidth of wave 1 devices and offer data transfer rates of up to 3470 Mbps.
Updated: July 24, 2013