A firewall is a security system that monitors and controls incoming and outgoing network traffic based on predefined security rules. It is an important component of a company's security infrastructure as it protects against unauthorised access and malicious attacks by enforcing security policies.

Firewalls can be hardware or software based and can be configured to allow or block traffic based on various criteria such as the source and destination of the traffic, the type of traffic and the port used.

Firewalls are used to protect networks from external threats such as hackers and malware and to prevent unauthorised access to internal networks. They are an important tool for protecting against cyber attacks and ensuring the security and integrity of a company's data and systems.