The connecting rod connects the piston and the

to transmit motion of the piston to the crankshaft

the function of a connecting rod is to transmit motion of the piston to the crankshaft.

piston pin

The connecting rod is attached to the piston by the piston pin.

journal

The connecting rod lower end is connected to the relevant journal of crankshaft.

I

The connecting rods are generally made of "I" shaped cross section.