Wifi, WiFi or Wi-Fi is a class of wireless local area network (WLAN) devices based on the IEEE 802.11 standards. Today, a wifi device is installed in many personal computers, video game consoles, smartphones, printers, and other peripherals, and virtually all laptop or palm-sized computers. Thanks Wikipedia.
When the APNK refers to wifi we are talking about the wireless technology that enables laptop users, etc, to connect to the APNK free internet service available at participating libraries.
See also -
Is the internet filtered?Information on the internet filtering in place on our PCs and wifi.