Many people actually misunderstood the function of the firewalls. People usually think that firewalls are used to block connections on certain ports or applications. That’s a part of firewall function but the main function of a firewall is packet analyzer or packet filtering like some people usually refer to. Routers can also be used to block specific ports using access list control or usually know as ACL.
To help you understand what firewall is all about, you can read this article titled Understanding Computer Firewalls. The article is really great in my opinion since it’s explained computer firewalls in plain English. So it’s really easy to understand even for people with no computer background. The article also talks about computer history briefly from the start of new age computer era and the emergence of computer viruses.
It also talks about why firewall came into the picture in the first hand when anti viruses can’t no longer cope with the worms and viruses which developed rapidly, growing fast and getting more complex each day. The article also explained what type of firewalls in the market these days, how it is implemented and why is it so important to have a firewall these days, even for a personal computer and not limited to only corporate networks.
Please take your time to read and understand the article. I hope you can get some new knowledge from the article and feel free to comment if you have anything to ask.