Wi-Fi, also know as 'wireless broadband', 'wireless networking' or 'wireless fidelity', simply means broadband without the wires.

The advantage of small, portable devices like laptops and PDA's is that they can be used anywhere around the house, but if you want to access the internet on them too you'll need a Wi-Fi transmitter.

Once you've got Wi-Fi, you can access the web anywhere in the house on any computer!

SOURCE  http://www.bbc.co.uk