Final answer:
Firewalls are commonly used to create network protection zones and protect network borders. They also provide security to hosts against attacks.
Step-by-step explanation:
Firewalls are commonly used to create network protection zones, to protect network borders, and at the host level to help armor the host against attacks. Firewalls act as a barrier between a trusted internal network and an untrusted external network, controlling and filtering incoming and outgoing network traffic based on predefined security rules. They analyze packets of data and determine whether to allow or block them based on these rules.