A network bridge is a device that connects two or more network segments, allowing them to communicate as if they were a single network. It operates at the data link layer of the OSI model, filtering traffic and reducing collisions by dividing larger networks into smaller, manageable sections. This helps improve overall network performance. Bridges use MAC addresses to determine whether to forward or filter data packets. By learning the addresses of devices on each segment, a bridge can efficiently direct traffic, ensuring that data reaches its intended destination without unnecessary delays.