Explain me the core network in networking

Can any one explain about core network in Networking...:!:

Hello brother

what do you mean by the core network
or example when we speak about the Ad hoc network exactly when we use the OLSR protocol we mean the core is the node which is the
original and which choose the MPR to it.


But when we speak about the switches and the wired network the core network is the switch which attach you directly to the routers

for example you have in the first layer the access layer when you connect your computer to the switch
and when the switch connects with another switch that means we are in the second later which called ......... I forgot it

and when the last switch connects to the router we call that the core layer or the core network


there are others typed of core network But what do you mean exactly by your question


thank you so much