Grass tennis is tennis which is played on grass. A famous grass tennis arena is the Wimbledon.
Tennis was originally played on grass courts.
The first surface tennis was played on was grass
lawn tennis is usually played on a lawn, which is grass
lawn tennis is tennis. It was the original name when tennis courts were made with grass
You probably mean "Lawn" tennis. Lawn tennis is simply tennis played on a grass court.
Clay And grass
Grass and Clay