What is a Cable/DSL Modem?
First of all, you need to understand what a broadband connection is and how it works. According to Dictionary.com, broadband is "a high-speed, high-capacity transmission medium that can carry signals from multiple independent network carriers. This is done on a single coaxial or fiber-optic cable by establishing different bandwidth channels. Broadband technology can support a wide range of frequencies. It is used to transmit data, voice and video over long distances simultaneously."
Instead of carrying a phone conversation or a television signal over these broadband lines, phone companies and television companies now allow data to be sent as well through DSL connections (phone service) and cable connections. Thus, you can hook your modem up to any cable outlet or phone jack and have instant Internet access (Just make sure the cable guy remembered to activate all your outlets).
In order for you to receive the information carried through the broadband connection, you must have a modem that delivers it to your computer. There are specific modems for DSL connections, and specific modems for cable Internet access. The difference primarily rests on the type of wire required to connect the modem to the outlet.
Choosing a Modem
Now that you know how a modem works, where do you find one. The answer varies between company, but phone service and cable service each have a general way of making sure you have a modem.
If you are getting DSL service, you will probably be buying your modem as you sign up for your service. Most of the time, you can get a discount by purchasing the modem from your phone company. Comparison shop, though, just to be sure you're getting a good deal. Also remember that with DSL, you'll probably be signing a year contract, so if you only request month-to-month service, you may not get the same discount price.
Cable companies provide a modem in a completely different way. Rather than having you purchase the modem, they often try to convince you to rent the modem from their company. At three to five dollars a month, this is a great deal if you don't expect to have the service permanently, but it's a terrible deal if you know you'll need Internet over the next few years. Sometimes, though, you can find deals through other companies on the Internet that offer discounted service from your cable company AND a free modem (after rebate, of course). Check out all the options and see which ones best fit your needs and save you the most money.
Now, there is just one more thing to discuss. If you are wanting wireless Internet, you will need to purchase a wireless router separately. You can find these at any Best Buy or Wal-Mart, and if you wait for a sale, you can get a good price. Before purchasing, though, make sure your computer has an Ethernet card - most laptops should come with this, but there are a few exceptions.
Once you receive everything, all you need to do is hook up your modem to the outlet and your wireless router to the modem. Now you can surf the Internet from anywhere in your home or even in your backyard!