Simply put...
Routers are OSI Layer 3 devices (Network layer - packets)
Switches are OSI Layer 2 devices (Data Link Layer - frames)
Switches connect LAN segments, use a table of MAC addresses to determine the segment on which a datagram needs to be transmitted, and reduce traffic.
Routers tie together, or interconnect network segments or entire networks. They pass data packets between networks based on Layer 3 information.
Protocols that support the network layer use a hierarchical addressing scheme that allows for unique addresses across network boundaries, along with a method for finding a path for data to travel between networks. While MAC addresses use a flat addressing scheme that makes it difficult to locate devices on other networks.
<A HREF="http://www.rad.com/networks/1997/nettut/protocols.html#OSI7" target="_new">Here</A> is a link to help.
The bottom line is that switches take on data differently to routers.
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"Now drop your weapons or I'll kill him with this deadly jelly baby."
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