WiFi

WiFi (or, for the nitpickers, Wi-Fi) is a term invented by a marketing firm as a play on the term 'Hi-Fi'. It is often thought of as being short for Wireless Fidelity, which doesn't really mean much, but is at least fun and trendy.

If you want to know more about the technology itself, visit the Wikipedia page on the subject: http://en.wikipedia.org/wiki/Wi-Fi