A plus (+) represents longer odds, in which case you'll win more for your wager, while a minus (-) means you're betting on a more likely outcome (as deemed by the sportsbook) and will win less when you emerge victorious. For example,R$100 on +110 odds wins youR$110, whileR$110 on -110 odds wins youR$100.
A spread of +7.5 means that the team must either win the game or lose by 7 or less points/goals/runs for the spread bet to win. A spread bet is a bet on the margin of victory with a handicap (or line) attached to it, in this case the handicap is +7.5.