A physical firewall is "a wall or partition designed to inhibit or prevent the spread of fire" and a car typically has one in-between the engine and the passeng

A physical firewall is "a wall or partition designed to inhibit or prevent the spread of fire" and a car typically has one in-between the engine and the passenger compartment. That way if the engine starts on fire, the passenger should have time to get out of the car before the fire gets to them. Computer firewalls are similar in that they are designed to protect the computer (the passenger compartment) from security threats (fire). Just like the firewall in your car, a firewall on a computer probably won't completely prevent security threats from getting through but it will help.