Arbitrage betting in sports is the process of simultaneously placing bets on all possible outcomes of an event. This needs to be done at odds that guarantee a profit.
Arb betting is a possibility when there is a discrepancy between odds that allow a profit to be made by covering all possible outcomes of the match.
Usually, this happens when the outcome is binary (i.e. win or lose) – with just two outcomes. An example would be a CS:GO match, where only two results are possible.
Arbing opportunities most commonly arise when bookmakers disagree on odds or make a mistake when pricing a market.