Can you explain me please what exactly does "Protected (2D)" proportional editing mode?

  1. Can you explain me please what exactly does “Protected (2D)” proportional editing mode?
  2. Also what is the difference between the “Connected” option and just “Enable”?

Thanks in advance!

Connected will calculate the influence over the surface, imagine it like it spreads over the surface based on how those verts are connected.

The regular method is just based on the projection of the brush (based on the size of it) under the mouse pointer. So this method might pick up stuff that is not in close proximity, since it does not care about connectedness and topology of the edited mesh.