Let’s define some basic concepts and elements of networks:
Internet
General Info about this medium
http://en.wikipedia.org/wiki/Internet
Intranet
http://en.wikipedia.org/wiki/Intranet
Extranet
http://en.wikipedia.org/wiki/Extranet
Wide Area Network (WAN)
http://en.wikipedia.org/wiki/Wide_area_network
A computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries).
Router
http://en.wikipedia.org/wiki/Router
