A firewall is a security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. It acts as a barrier between a trusted internal network and untrusted external networks, such as the Internet. Firewalls can be hardware-based, software-based, or a combination of both, and they help protect computers and networks from unauthorized access and cyber threats. Firewalls can filter traffic based on various criteria, including IP addresses, protocols, and ports. They can also log traffic data for analysis and alert users to potential security breaches. By implementing a firewall, organizations and individuals can enhance their cybersecurity and safeguard sensitive information from malicious attacks.