A term for a broad category of network components that allow communication between different networking architectures and different protocols. Gateways generally operate at the higher levels of the Open Systems Interconnection (OSI) reference model for networking. They are commonly used to provide connectivity between two different protocol stacks that might be running on different systems.
Examples include the following:
A gateway is usually a dedicated device or a set of services running on a dedicated computer. Gateways are essentially devices that direct network traffic in some fashion and translate that information.