A bridge operates at the data-link layer of the OSI Model for computer communications. It manages the flow of traffic between the two LANs by reading the address of every packet of data that it receives.
A gateway is a shared connection between a LAN and a larger system, such as a mainframe computer or a large packet-switching network, whose communications protocols are different. It is usually slower than a bridge or router. It is a combination of hardware and software with its own processor and memory used to perform protocol conversions.
This was first published in February 2003