Most Finishes applied to floors today are either urethane based (which is actually plastics ) or water-borne finishes.

Urethane Finishes
These finishes go on thicker that water borne so less coats are needed.  The coats are sprayed on.  Usually seven coats are applied

Aluminum Oxide Finishes
This is a urethane based finish with finely ground aluminum added for extra scratch resistance.  A 220 grit paper should not be able to scratch the floor.  Almost the hardest finish today

Moisture Cure
The hardest finish available.  It is toxic and calls for a respirator.  Cannot be done in the factory