The unique, weighted system of the NBA draft in which non-playoff teams from the previous season participate to determine the order of the draft.
Under the rules of the NBA, 14 teams participate in the lottery system and are referred to as "lottery teams." The lottery system is weighted in such a way that the team with the worst record in the previous season (or a team that possesses the draft rights of said team) has the best chance to receive the first draft pick. The lottery involves using a lottery machine containing ping pong balls numbered 1 to 14, and is then weighted by possible combinations of four number groups, with the most chances going to the highest seeded team (250 combinations; 25% chance) on down to the "best" non-playoff team (5 combinations; .5% chance). After all lottery team picks have been selected, the draft continues in the usual manner, by win-loss record in reverse order. Subsequent rounds do not involve a lottery.
The current lottery system has been in place since 1995.