The plus sign (+) means "ADD" in programming and on calculator keyboards. For example, 10 + 7 means 10 added to 7. It is also used as a concatenation symbol for text fields. For example ...

American odds are formatted to represent either how much money you must risk to win $100 (if there’s a minus sign) or how much money you’d win on a $100 wager (if there’s a plus sign).