Gateway

Gateway is a term with multiple meanings depending on context. In architecture and urban design, a gateway is an opening, entrance, or passage that marks a boundary between spaces or districts and often serves as a symbolic or functional point of access.

Computing and networking use the term for devices or software that connect networks and enable communication between them, especially when different communication protocols or data formats are involved. A network gateway operates at the edge of a network, routing traffic between networks and often performing protocol translation, data encapsulation or de-encapsulation, and security functions such as filtering.

Common types include traditional network gateways, gateway routers, or gateway appliances that combine routing, firewall and NAT, and VPN gateway devices. A gateway can also function as a protocol gateway that translates between, for example, Ethernet and legacy serial or between IPv4 and IPv6 or other application layer protocols.

In commerce, a payment gateway is a service that authorizes and processes payment transactions for online retailers, handling sensitive data and communicating with financial networks.

History and terminology: The word gateway reflects its role as a controlled doorway between spaces, and in modern networks the concept is broader than a router, encompassing any device or service that mediates access between disparate networks.