A node on a network that serves as an entrance to another network. For example, when a user connects to the Internet, that person essentially connects to a server that issues the Web pages to the user. These two devices are host nodes, not gateways. In enterprises, the gateway is the computer that routes the traffic from a workstation to the outside network that is serving the Web pages. In homes, the gateway is the ISP that connects the user to the internet.
In enterprises, the gateway node often acts as a proxy server and a firewall. The gateway is also associated with both a router, which use headers and forwarding tables to determine where packets are sent, and a switch, which provides the actual path for the packet in and out of the gateway.