first of all… what model of laptop do you have? are you sure it doesn’t have wireless ethernet capability (wifi) built in? (if not, you need an adapter … usb or pcmcia… don’t spend more than $40US… you can probably find one for around $20)
second… do you already have an internet connection in your house? if you have DSL or Cable internet then you probably have a DSL or Cable modem… depending on how new your modem is it may or may not have wirless ethernet (wifi) capability built in… call your Internet Service Provider (ISP) to find out. If it does NOT have wirless eithernet. You will need to buy a separate wireless router (if your modem has only one Ethernet plug) or wireless access point (if your modem has more than one Ethernet plug)
optionally, instead of buying a router or access point you could also buy a wifi device for your main computer that is always connected to the internet (either a USB adapter like you’d need for your laptop… can even be one just like it. or a PCI adapter that has to be installed inside your computer… not a good idea if you’re not a technical person) Then you can share your internet connection through your main computer with your laptop.
This setup may be cheaper… but you will need to have your main computer turned on and logged-in in order to use internet on your laptop.
good luck

the best lappy brand alienware but they are expensive so then hp do you have a router? you need one of those i reccomend the belkin g+ mimo pretty much all lappys come with wireless cards these days