Wi-Fi

Wi-Fi is a trademark of the Wi-Fi Alliance, originally founded in 1999 as WECA (Wireless Ethernet Compatibility Alliance). The organisation comprises more than 300 companies, whose products are certified by the Wi-Fi Alliance, based on the IEEE 802.11 set of standards (also called WLAN (Wireless LAN) and Wi-Fi). This certification grants the interoperability between different wireless devices.
The alliance was founded because in many products the IEEE 802.11 standards were not implemented correctly or entirely, and some included proprietary extensions. This led to many incompatibilities between products from different manufacturers.
The Wi-Fi Alliance tests the wireless components by their own terms of reference. Products that pass the test get the Wi-Fi certificate and are allowed to wear the Wi-Fi logo. But only the products of the Wi-Fi Members are being tested, as they pay a membership fee and a per-item-fee. According to that, a missing Wi-Fi logo does not necessarily mean an aberration from the standard.
In some countries (USA, France, Poland...) the term "Wi-Fi" is often used by the public as a synonym for wireless internet (W-LAN), although not every wireless internet product has a Wi-Fi certification. This is due to certification costs that have to be paid for every single certified device.
Wi-Fi certification is provided for the wireless technology used in home networks, mobile phones, video games and other electronic devices that require some form of wireless networking capability. In particular, it covers the various IEEE 802.11 technologies (including 802.11a, 802.11b, 802.11g, and 802.11n).
Wi-Fi certified technologies are supported by nearly every modern personal computer operating system, most advanced game consoles, laptops, smartphones and many printers and other peripherals.