Why a firewall can be your computers best friend (and why you need it).

Think of a computer based firewall like the great wall of China. A computer firewall is a barrier between you and the internet. It filters the good from the bad (hacking attempts). You need it to prevent people from hacking into your computer, and to prevent virus' and spyware from spreading in your network. 

However there are over bearing computer firewall software like Comodo's firewall. Trust me, you don't want to put software on your brothers/mothers/friends computer that asks a mother may it connect to the internet (it's why people hate vista!). The firewall that is included in Windows/Mac OS X does a very good job. 

If your router has a firewall it's self then it's all you need. Hardware based firewalls will do the job very well. 

You will always need a software firewall (like Windows firewall) when you are out in public in-case they don't have a router firewall.

No firewalls are perfect but they do help you from the parts of the internet that just don't belond. No one likes there computer being hacked into by someone somewhere else.