Coplanar circles that have a common center are called

Concentric circles

Step-by-step explanation:

They are co-planar, so they lie in the same two-dimensional space.  Since they share a common center, they would only differ in radius length.  What we would have is a bunch of circles withing other circles sharing a common center.  We call those concentric circles

Con- with

Centric - having to do with the center