Firewall is the term used to describe protecting devices.
Be it protecting a building or vehicle from prospective danger of fire or a computer network from dangers, firewalls are used as barriers to protect them.
In terms of computers, firewalls are a technical barrier used either in software or hardware forms.
If they are being used in software forms, they are like software programs that will protect work being done on that machine.
These types of firewalls are ideal for home based networks where work is done generally on a single or maximum 2 machines.
Hardware type firewalls come in a separate hardware which can be attached to the network to perform.
Such firewalls are generally used in big companies where lots of machines are being used at same time and lots of data needs to be checked for protection.
They could be in form of box or a machine.
Firewalls are very important for any machine that is connected to internet.
Nowadays, no computer is safe from viruses, Denial of Service (DOS) attacks, hacking and worms.
An unprotected computer becomes the target of all the unscrupulous people to perform all illegal and unwanted tasks without the knowledge of owner of the machine.
The hackers today can hack into any machine and perform God only knows what.
Firewall protects computers from Remote Login where nobody will be able to connect to your computer and control it.
They protect you from backdoor applications which mostly are bugs only.
Sending spam mails is one of the most beloved tasks that can be performed using your server.
Firewall controls this to large extent.
Email bombs are another way of crashing your system.
In this a hacker sends you a same mail in bulk which ultimately crashes down your server.
There are many kind of firewalls available in market today.
A basic firewall will protect your computer with a limit whereas a highly technical firewall can provide a large amount of security.
Choosing a right firewall depends upon your preference and needs.