WiFi is a Wireless Local Area Network (WLAN) technology which uses unlicensed radio signals, typically in the 2.4 and 5GHz bands to connect devices such as computers, laptops, tablets, cellphones, PDAs and CCTV cameras to central infrastructure WiFi Access Point (AP) devices.
WiFi is commonly used as an indoor coverage scenario in business, government and residential applications to provide internet and Local Area Network (LAN) connections
WiFi is generally a Point to Multipoint (P2MP) architecture using Access Point (AP) and client devices. Some devices can also operate in Point to Point (P2MP) and Mesh architectures
Outdoor networks can extend WLAN coverage outside to cover public spaces such as public parks, business parks, marinas, golf clubs, resorts and beaches.
Today, Wi-Fi is in 25 percent of homes around the world, and about two billion Wi-Fi devices were sold in 2013. The original WiFi devices were certified in 1999 with 11Mbps raw capacity. New frequency bands below 1GHz are being considered, and higher frequency bands such as 60GHz also.
Examples of commercial WiFi products can be seen here