You hear about firewalls in reference to computer hacking when you watch espionage movies, but what is a firewall? It is, in essence, a security device that walls off your network from outside intrusion. A firewall exists in front of every corporate network, blocking access to internal resources and acting as a sentry for the type of connections that are allowed to go in and out of the network. It may sound complicated and highly technical, and that is because it is highly technical. You would not employ such a device in your home, but just because you would not use a corporate grade firewall in your home does not mean that you have to go without protection.
There are firewall programs that can be installed onto your personal computer. They have a similar goal as a high cost firewall appliance in that they aim to regulate the flow of traffic in and out your computer on specific ports. It also allows you to be stealth, in that anyone who attempts to find your computer is not denied access, but is merely ignored. This way they will not even have confirmation that your computer is indeed there, which adds greater invisibility and protects you from attack.
For those who utilize a home wireless network, a firewall service is built in to the wireless routing device. This should not be considered a complete replacement for a personal software firewall, rather, it should be ran in conjunction with a software firewall to maximize the level of protection. And just like with an expensive business class firewall, your computer will be protected from many forms of intrusion from outside parties. No firewall is infallible, but television and movies make it appear that firewalls are easily breached. Configured correctly, trust that they are not.