A routing table is an information database that is contained within a network host. It lists the routes that different network destinations should take. The table will include information about the network topology directly connected to the host, and therefore allows numerous networks to interconnect. These networks can either be private local networks (LAN) or larger networks (WAN) which connect over the internet.
The primary purpose of a routing table is to ensure the information being sent is sent via the most efficient routes, but it can also include backup routes. This means information doesn’t clog up the network resources of devices where the data isn’t needed.
Every network will use a routing table in some manner. Fortunately, most smaller networks benefit from the fact that a single device will automatically configure the routing table on your behalf. Larger and more complex networks which spread across more than one device will often require some user input to specify network paths, and device locations.