If one can consistently make bets where the odds of paying out are better than the true odds of the event, then over time one will come out ahead.
In the parimutuel world, there are two categories of odds lines which reflect the
probabilities of an event’s outcome: morning line odds (MLO) and post time odds (PTO).
Neither the PTO nor MLO represent the true chances that the event will occur. PTO are the amounts that will be returned on winning bets. MLO are a prediction of PTO.
These two odds lines are constructed by unique ‘linemakers.’
The PTO linemaker is the betting public.
The MLO linemaker is an individual.