Well.......
A HUB is more or less a boxed formof early "bus networking" where computers were all connected to the same "network wire" and listening for activity and data collision was the job of the individual network adapters...
EARLY BUS ARCHITECTURE
computer 1 computer 2 computer 3
|____________|___________| <- network wire
This is what a Hub actually does...
A switch is a little more complex... but I won't go into that as it is way off topic...
A router is a little more than a hub or a switch... It actually handles data translation accross the network nodes and can even have some "smart" features enabled such as IP traffic blocking, DHCP, and yes, even internet connection sharing...
But as it was said in the 1st reply... there are better places to learn about stuff in detail than a forum...
Squirrelly1