Your Gateway or Router Address tells your computer which device on it's network is responsible for sending traffic out to the Internet. Your Gateway Address is often given to you with a Subnet Mask, IP Address and DNS Addresses. This set of information tells your computer how to find things on the Internet.
A gateway address is the I.P address of a network point that acts as an entrance to another network. For example, in a corporate network, a proxy server or a router acts as a gateway between the internal network and the Internet.
The address of the gateway used to reach a specified destination; for example, on a network or the Internet. Gateways are devices that route packets between different physical networks.