What is a firewall and why is it necessary?

The main reason why we every computer needs a firewall is that as it is a software or a hardware where hardware is found in routers and software are found in Computer. When you have a firewall installed in your Computer would be protected from unwanted websites and hackers. It monitors the incoming and outgoing networks and block the unwanted and malicious networks to access your PC. So every computer needs to be shielded with a firewall. Get them to always block unauthorized network users. This is the reason why a firewall is necessary software or hardware program.