The role of a firewall in cybersecurity is to monitor and control incoming and outgoing network traffic based on predetermined security rules. It acts as a barrier between trusted internal networks and untrusted external networks, such as the internet. Firewalls can be hardware-based or software-based, providing essential protection against unauthorized access, cyberattacks, and data breaches. They also facilitate the creation of virtual private networks (VPNs) and application layer protection. By filtering traffic and blocking potential threats, firewalls play a crucial role in maintaining the overall security posture of an organization.