How was gambling used in the book?

chapter 1:

Charlie and the others then meet Squizzy Taylor, a physically small but powerful street criminal. One of the boys, Barlow, bullies Charlie, but he pays more attention to Squizzy and to Dasher, who give the boys their assignment – deliver a parcel of two unbroken eggs to an address across town. Bets are placed as to which of the boys would be fastest, with Charlie having the worst odds.