Nearly all current laptops come equipped with built-in facilities for WiFi communication. Even if your laptop doesn’t have the latest technology, you can upgrade it for WiFi.
You have several good solutions:
Install a WiFi adapter in a PC Card or Express Card slot. If you go this route, you’ll have to learn to take care not to damage the small nub of an antenna that extends from the end of the adapter; it is easy to break off and destroy the card or even damage the slot of the laptop. It’s also important to turn off the power to the card when it is not in use. You’ll also be dedicating one of a limited number of slots on your laptop to a single purpose.
Replace the built-in adapter with a new unit certified by the original equipment manufacturer. If you replace the built-in hardware, you will have to carefully follow instructions mandated by the Federal Communications Commission (in the United States) or the equivalent in other countries; they do this to avoid the possibility of interference with other radio systems.
Add an external WiFi adapter that connects to your laptop through the USB port. You may have problems with this solution if your laptop has USB 1.0 or 1.1 ports instead of the more advanced and speedier USB 2.0 design. This solution has two designs: One is a simple device, about the size of a pack of gum, which plugs into the port and extends out to the side; the antenna is built into the case. The other is a small external WiFi transceiver that attaches to the laptop with a USB cable.