Finishing a floor essentially means the treatment you put on after the sanding process. The icing on the cake if you like. It is the stage that offers protection to the wood underneath and is vital in the overall aesthetic of the floor. Just don't say varnishing.
Lacquer has been around since ancient times and derives from the Sanskrit for 100 000 and the Lac beetle, which congregates in huge numbers. It was the secretion from these poor beetles that was used as a finish for wooden products in India. Times and animal welfare awareness have moved on since then. Today, lacquers are highly durable water-based products that finish floors with minimal effort and maximum effect.