(Standard and Expert modes) The Path Constraint constraints the position of a layer to any Bézier path (CC2018 and up only).

1. Select a Bezier path
2. Click on the "Pick Path" button of the Path Constraint panel
3. Selec the layer to constrain
4. Click on the "Create" button

A "path constraint" effect is added on the layer, where you can animate the percentage to move the layer along the path.

NOTE: the position of the layer can still be animated, and you can move it yourself to the path if you want it to be exactly above. In this case, set the percentage to 0% and move the layer above the first vertex of the Bezier path.

If the path itself is animated, the constrained layer will follow the animation of the path, even when the percentage is animated.