Switch
In computer networking, a switch connects multiple network devices together to form a LAN. A switch works by filtering and forwarding packets between LAN segments, transparently bridging them.
A switch is essentially a more efficient, sophisticated hub.
Not a router
A switch is often confused with a router, but the two serve very different purposes. While a switch connects network devices together to form a LAN, a router determines the best way to route packets across networks, based on certain network conditions.
The confusion probably stems from the existence of devices which act as both routers and switches.
Neighborhood Analogy
A good analogy for switches and routers is to think of a network of computers as a neighborhood. A switch is the street which connects the houses, and routers are intersections which connect the neighborhoods and contain important information about them, like street names.
