how service parts are mapped with service confirmation or serv prod and serv contracts

i created one service contract and entered my service product and component as well.

Now i have created service order as a follow up of my service contract and created service confirmation with service part as we..

But if you see i didnt maintain service part in my Ibase which i used in my service contract.

i dont have clear idea about how my service parts are linked to my service confirmation or service order or contract..

thanks