Each system has its own routing table. The kernel maintains the routing table of a system. The Routing Table basically decides or controls where and how packets will be sent from the source to the destination. It decides which path the packets will take i.e. it decides as to which router should the system pass on the packet to. Communication through the Internet takes place, using routers.
Routers are basically systems, which connect two networks together.
They are commonly used to connect an internal trusted network to the external un-trusted network called the Internet. ISP s use routers to connect you to the Internet. Routers basically act as gateways to the Internet or gateways to external networks. The Routing Table of a system besides holding other important useful information stores the router address to which packets have to be transferred, depending upon the IP Address of the destination. Let us look at the routing table of a typical machine to understand better.