English n sports betting, a banker (or "bank" in some cases) is a term that refers to the most reliable bet in an accumulator or a series of bets. It is considered that the likelihood of winning this bet is extremely high. Typically, when a player includes a "banker" in their accumulator, the other bets may be riskier, but this selection is added as a guaranteed or almost guaranteed win, which increases the overall chances of success for the entire accumulator.
It is important to understand that even a "banker" does not guarantee a 100% win, but it is generally perceived as a low-risk bet. To place a risk-free bet, you can use the arbitrage betting strategy.