@waylow is the best person to answer this question, but I’ll have a go.
There is a great example of constraints in the Blender manual, I will try to explain it here.
They can make the eyes of a tennis player track a tennis ball bouncing across the court
A Damped Track constraint added to the eyes (or control bones for the eyes in the armature) of the tennis player, so they are looking towards the tennis ball wherever it is on the tennis court.
If you was to parent the eyes to the ball, the eyes will not only look in the same direction as the ball, but also follow the ball location, as if the eyes are attached to the ball. The child (eyes) will copy all the transforms of the parent (ball), location, rotation and scale.
I have a phrase when I try and explain the parent/child relationship in Blender
“A parent will take the child wherever they go, however the child can also wander from the parent”
In this case, the ball can move around the court taking the eyes along with it, but the tennis player can pick up the eyes and put them back where they belong leaving the ball on the ground.
Hope this makes sense!
