Do you have access to the internet via broadband already ?
If so then the wire comes into your house into a modem, then a wire goes from the modem to your laptop.
That is called WIRED internet.
To make this wireless you need to buy a piece of hardware called a ROUTER, in fact a WIRELESS ROUTER.
You then take the wire that currently come OUT the modem and goes into your laptop, and you plug that into your router.
The router then sends a wireless signal OUT that is then picked up by your laptop.
So the path is PHONE LINE to MODEM to ROUTER then wirelessly to your LAPTOP.
You should not need to install or buy any extra software if you are running Windows XP to use wireless as it is built in.
I would contact your ISP (if you have one) and ask if they have a wireless router, they will also probably have a setup CD that will set everything up for you.