* The exterior door handle: This is what you physically grab to open the door.
* The interior door handle: Also used to open the door from inside.
* The linkage rods and levers: These are inside the door and connect the handles to the latch mechanism.
* The latch mechanism: This is the part that actually engages and disengages with the striker plate on the door jamb.
To find the connection point you'd need to remove the inner door panel. The linkage will be visible once the panel is off, showing how the handles connect to the mechanism that operates the latch bolt. You'll see the rods and levers connecting to various points *on* the latch itself. There isn't one single "connection point" but rather a system of interconnecting parts.