shy
d'ya mean a router or a router?
a "real" router connects separate network (subnet) segments together to form a mesh ... (you asked!!)
the basic question is ... is this for my office ..or somewhere else - if somewhere else ... pass it to the next office .......
until eventually someone will accept it and pass it to the right machine
so the scotland, yorkshire, birmingham and london offices (each with 10 employees (or floors 1-4) can talk to each other and between branches - instead of just having 1 big pool - by routing traffic round the mesh more efficiently if scotland is buisy ... it won't affect traffic between birming and yorks... if yorkshire goes down you can still route to london via birmingham.
a domestic router (yours) is actually a full blown server (not bad for �50!) which provides quite a number of extra services
it routes (is this request for one of OUR other machines - if not pass it out on the internet)
it gives out IP addresses when a machine is switched on (dhcp)
it passes your request for bbc.com to the internet ... and then makes sure you get the archers and not the barclays bank request places by your son (nat).
it makes sure that bbc.com is translated into the number based address that the internet requires (dns)
it probably acts as a firewall.
it runs your wireless connections
it handles security wep, wap or whatever
a bt home hub also manages your telephones like a simple switchboard
and will act like a fon station
as well as connecting an internet anywhere handset to the outside world
oh and it connects you to the internet via the exchange (modem).
so actually ... it does far more jobs than your PC ... in a smaller box. .... and rarely ever makes itself obvious
if you look on the net there are a lot of people hacking their "router" to make it do even more amazing