The proximityPin node is used to track positions on a deforming surface. It derives positions from the closest points on a surface from the input transforms. By contrast, the uvPin node derives positions from specified UV coordinates. Use the proximityPin node to attach objects to your geometry when you want to controls for repositioning inputs, or when clean UVs are not available.
As the proximityPin is procedural, you can make changes to the inputs, coordinate system, alignment, and offset after creation.
See Create a proximityPin for steps on how to use a proximityPin node to attach objects to your geometry.