A double-double is when a player records 10 or more in two of these categories: points, rebounds, assists, blocks, and steals.
A triple-double is 10 or more in three of those categories.
For example: a player finishing with 24 points, 11 rebounds, and 6 assists has recorded a double-double. If they finish with 24 points, 11 rebounds, and 10 assists, it's a triple-double.