Hello,

Both means the same. Coast line and shore line has same meaning. It means the contour or outline where land meets coast of sea or ocean which we say beaches. There are places where outline place have forest , home.

Coast line area means the first place which will get effected by the ocean. If any natural disasters like cyclone is tsunami comes , it will effect coastline/shoreline areas.

Coast line basically reffers to outline of continent or island. Shoreline can reffers to any waterbody like pond, river or lake where water meets land. The bank of any water body is called as shoreline.

Hope it helps!