Whereas negative (-) odds tell you what you have to bet on the favorite to winR$100, positive (+) odds tell you how much you'll win for everyR$100 you wager on the underdog. So, a team with odds of +120 would payoutR$120 for everyR$100 wager.
So, a bettor looking to winR$100 will riskR$180, while a bettor looking to winR$50 would wagerR$90. Remember the amount you wager remains with the sportsbook if your side loses, while a winning bet returns your winnings and initial investment.
To many poker players and fans of the sport, the term "pro" simply means top player in the field. Depending on the level of competition in any event I am playing at, I have experienced both sides of this example of the definition: where I am looked upon as the pro at the table and where I am sitting amongst pros.