A triple-double in basketball is when a player achieves double digits in 3 or more of the following statistical categories:

Points

Rebounds

Assists

Steals

Blocks

So for example, if a player scores 15 points, has 10 rebounds and 11 assists – they have a “triple double”. If the same player only had 9 rebounds, this would be a “double double” – because they reached double digits in only 2 categories. The most common combination for a triple double is points, rebounds and assists. 

The current all time NBA leader or Triple Doubles is Russel Westbrook.