A router is a computer whose software and hardware are designed to move data between computer networks. Routers move traffic to where it needs to go. They do this by choosing the shortest path between the computers using a complicated system of rules called routing protocols. Most routers have a specialized operating system, RAM, NVRAM, flash memory, and one or more processors. They also have two or more network interfaces. They come in a variety of sizes from something that could hold in the hand to something too large for one person to lift.