There are many different types of firewalls available to consumers and corporations alike, and while each firewall is different, they all have some things in common. This tutorial lists these features they have in common and their use.

Block incoming network traffic based on source or destination
Blocking incoming traffic is the goal of all firewalls.

Block outgoing network traffic based on source or destination
Many firewalls can also filter traffic coming from your network to the internet. This can be used to prevent employees or children from accessing inappropriate websites.

Block network traffic based on content
Most firewalls can also filter traffic for inappropriate content. For example a firewall containing a virus scanner can prevent files containing viruses or other malicious programs from entering your network. Other firewalls contain email filtering capabilities to filter out inappropriate email messages.

Control access to internal networks
Some firewalls allow you to setup and control access to virtual private networks (VPNs). VPNs allow secure connections from the internet to a corporate network

Track network traffic and firewall activity
While keeping your network safe, a firewall silently keeps a log of everything that goes on. Such as who access inappropriate material, or who tried to break in. This information can be extremely useful when something goes wrong. Every firewall comes with some kind of tracking or reporting utility.