So the replica is a full copy of the original parent image. The linked clones are assocaited/linked to the replica to provide the base of the OS. The linked clones represent the different/customization of the base image. We use the replica so the master/gold VM can be used for something else without having a direct link to it. DO NOT do anything with the replica. If it is deleted, your linked clones will stop working.
When I teach View in the classroom, I put it forward like this:
Imagine a VM with a snapshot that is active. Now imagine that we have that same snapshot active 200 times. That's essentially linked clones.