The game was associated with traditional Hindu philosophy contrasting karma and kama, or destiny and desire. It emphasized destiny, as opposed to games such as pachisi, which focused on life as a mixture of skill and luck.
The ladders represented virtues such as generosity, faith and humility while the snakes represented vices such as lust, anger, murder and theft.
In the original game the squares of virtue are: Faith(12), Reliability (51), Generosity (57), Knowledge (76) & Asceticism (78).
The squares of vice or evil are: Disobedience (41), Vanity (44), Vulgarity (49), Theft(52), Lying (58), Drunkenness (62), Debt (69), Murder(73), Rage (84), Greed (92), Pride (95) & Lust (99)
These were the squares where the snake waited with its mouth open. The 100th square represented Nirvana or Moksha. The tops of each ladder depict a God, or one of the various heavens (Kailas, Vaikunth, Brahmalok) and so on.
The morality lesson of the game was that a person can attain Moksha through doing good, whereas by doing evil one will inherit rebirth to lower forms of life.
The numbers of ladders was less than the number of snakes as a reminder that a path of good actions is much more difficult to tread than a path of sins.
Presumably, reaching the last square number 100 represented the attainment of Moksha (liberation from the cycle of death and rebirth).
