From the looks of things here, there’s not much special going on. The only important thing to note is that the Suzanne head has a constraint on it. However, you can Grab (G) and move the head around all you want. But, select the circle object (right-click) and Tab into Edit mode. There should be a single vertex selected right where the Suzanne head is. That vertex is the sole member of a vertex group call Group. If you Grab (G) that vertex and move it around, the Suzanne head will follow it.
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