Firewalls are specialized softwares used to protect privacy and security of users of network connected computer by controlling inbound (inward) and outbound (outward) data traffic.

Firewalls come in two different forms:

1. Software based firewalls
2. Hardware based firewalls

Firewalls can be additionally classified into two other categories. Firewalls used on client computers and ones used on server computers.

Server computer are machines that provide services to other computers through a network. The computer receiving the services is called a client computer.

Firewalls used to protect server and client computers essentially function identically, but ones created for client computers are usually much more sophisticated and enable the users to fine tune the security settings based on personal needs.

On the other hand, server computers provide a wide range of services for client computers and increasing security level in a server computer means decreasing level of functionality provided, so server computers are always prone to intrusions and abuse attempts made by malicious users connected to servers through other computers, because fine-tuning the amount of functionality provided and the amount of security based restrictions in a server computer is an art that not all system administrators are aware of.

Firewalls produced to be used on client computers often provide comprehensive set of  security and privacy related features.

Users should fine tune the features to benefit from what a certain firewall offers. Some firewalls come as a package integrated with an antivirus software.

Some tips about firewalls:

1. Some firewalls come integrated with antiviruses. It is a very good idea to use only one antivirus in active and resident form (active memory resident shield) to avoid conflicts. You will need to disable active shield or guard of antiviruses except the one you want to serve in active form if you have more than one installed on a single computer.
2. Firewalls function based on defined rules, like blocking a certain port or allowing a certain program to access the Internet and most of the sophisticated firewalls ask users to allow or block connections. It is very important to read messages provided by firewalls carefully and make decision subsequently to block or allow a connection request.
3. Update your firewall immediately if there is an update available.
4. Fine-tune security settings of your firewall based on your specific needs. An expert's help would be very useful if you are not experienced enough.

The link to the web site of Comodo firewall comes below:

http://www.comodo.com/home/internet-security/firewall.php