WiFi is a universal wireless networking technology that utilizes radio frequencies to transfer data. WiFi allows for high speed Internet connections without the use of cables or wires.
The term Wi-Fi is a contraction of "wireless fidelity" and commonly used to refer to wireless networking technology. The Wi-Fi Alliance claims rights in its uses as a certification mark for equipment certified to 802.11x standards.
Wi-Fi is a freedom, freedom from wires. It allows you to connect to the Internet from just about anywhere - a coffee shop, a bed in a hotel room or a conference room at work without wires. And the best thing of all, it's super fast - almost 10 times faster than a regular dial-up connection. Wi-Fi networks operate in the unlicensed 2.4 radio bands, with an 11 Mbps (802.11b) or 54 Mbps (802.11a) data rate, respectively.
To access Wi-Fi, you need enabled devices (laptops or PDAs). These devices can send and receive data wirelessly from any location equipped with Wi-Fi access.
What is Next ?
Now the focus in wireless is shifting to the wide area. WiMax, short for Worldwide Interoperability for Microwave
Access, is defined in IEEE 802.16 standards is designed to deliver a metro area broadband wireless access (BWA) service, and is being promoted by the WiMax Forum.
WiMAX is similar wireless system to Wi-Fi, but on a much larger scale and at faster speeds. A nomadic version would keep WiMAX-enabled devices connected over large areas, much like today's cell phones.
For more detail on WiMAX you can go through WiMAX Tutorial.