Reason number two that the bookie wins: He “charges” people to bet. The odds that he offers don’t add up to an implied probability of 100%, the remainder being potential profit for the bookie (known as the “vig” in the US). Depending on the event he might be charging a couple of percentage points (so on average he’ll make $2 for each $100 bet) to a couple of hundred percentage points (so on average he’ll make $200 for each $100 bet). It depends on his certainty around his estimate, how dodgy he is, how dumb he thinks his punters are, how much competition he has, and so on.
Straight-up bets, also known as the moneyline, are picks that are made on one club triumphing over the other. If Manchester City is playing Watford, in order to make a moneyline wager you’d need to pick one of those clubs to win. If you choose Man City and they do win, you’d win your moneyline bet. If the inverse happens and Watford wins, you’d lose your moneyline bet.