The memory controller chip North-bridge and input / output controller chip South-bridge circuits are placed on the motherboard.
The internal components ( CPU , main memory RAM , Graphics Card ) are connected through North Bridge.
And other peripheral devices ( Display monitor , printer , keyboard , mouse ) are connected through the input & output controller chip South Bridge.
All these components are connected by using the system of bus wires which essentially carries three different types of information :
1. Memory Addresses , 2. Control Instructions And 3. Data.