When I place a pad, there is an option Plated. Here is the picture
What is the difference between plated and unplated pad without hole?
There is no difference. The setting applies to plating of the hole, where there is one.
A plated hole is lined with copper; an unplated hole is not. For example, clearance holes for mounting screws or standoffs might be specified as unplated, whereas holes for through-hole components are always plated. Plating the walls of the hole ensures electrical contact with inner layer traces that must connect to the pad.
Note that unplated holes typically add cost, as the hole must be physically plugged during the plating process.