Probability is the chance, likeliness or odds of an event occurring. It can be determined using statistics from sample data. Basically, probability is a part of a whole. It is always expressed in terms of fractions or percentages.
With that being said, I think the probability given in your problem is 1/19. This means that in every 19 bets, you have a chance to win once. If the probability of winning the roulette is 1/19, that means that you have a 1/19 or 5.3% chance of winning. Therefore, the actual odds of winning the roulette is also 1/19.