For example, if a team has double the chances to win, then the house instead of paying you 2X, they will offer to pay 1.9X for example.
That means that over a long period of time, they pay you less for the amount of risk you're taking.
Imaging that you're doing a coin flip and you guess what side of the coin will be selected, if you guess it right, I pay you slightly less than your bet. Over the long term you'll run out of money, because your expected return is negative.
So in sports betting, what I meant, is that a player can only win or lose a bet based on the outcome of the game which is not controlled by the casino or any mathematical calculation or algorithm.