It has two modes: Climb mode, Time mode
Climb mode: You have to complete every level without failing or you start over, each level earns you one point. The person who completes to most levels will be on top of the leaderboard.
Time mode: You have to complete every level in a time limit based on your board's difficulty. Each level earns you as many points as much time you had left on completion.
The person who completes the levels in the least amount of time will be on top of the leaderboard.
You have to sign in with your Google Play account in order to access the leaderboard, in case you don't have an internet connection or you don't want to sign in, your high score will be saved locally on your device and you can check it in the "My Stats" panel. Otherwise, the "My Stats" panel will show your actual score from the leaderboard.
Don't forget to rate the app, thanks for playing!