0A default gateway is an IP router that networked devices use to send information to a device in another network or the internet. Default simply means that this gateway is used by default, unless an application specifies another gateway.
A default gateway allows devices on a network to communicate with devices on another network. Without it, the network is isolated from the outside. Basically, devices send data that is bound for other networks (one that does not belong to its local IP range) through the default gateway.
Consider an example below:
Network 1:192.168.1.0/24
Network 2:192.168.2.0/24
If host A in network 1 wants to send data to host B in network 2,it needs a rouer that knows how to reach network 2, that router is IP router 1 which functions as a default gateway for network 1. Similarly IP router 2 functions as a default gateway for network 2.
