A Grand Slam is a tournament of the ranked players and it spans across different continents. There are 4 Grand Slams in a year. The ATP is the Association of Tennis Professionals.
The Grand Slam is a tennis tournament, while the ATP is an orginization. (Association of Tennis Professionals.)
The USTA Southern Section League tennis Sectional tournament held at the Mobile Tennis Center featuering 60 tennis courts and over one thousand participants
The Australian Open
11 hours and 5 minutes.