Firewalls and Routers
Do you currently have a network set up? How do you know some hacker is not trying to break into it? How do you know he/she is not already in? Installing a firewall will protect you local network and computers from the crazy Internet.
Do you have more than one computer on your network and only one Internet connection? Do you want to allow that other computer to access the Internet? With a router you can allow as many computers as you would like to use one Internet connection.