The average result of a bet if it were repeated many times; a positive expected value means the price is better than the true probability implies.
Expected value compares a bet's payoff against its probability. When a model's estimated probability of an outcome is higher than the probability implied by the odds, the bet carries positive expected value — it is priced better than it should be. Negative expected value is the reverse, and is what the house edge represents.
Expected value is a statement about the long run, not any one bet. A positive-expected-value bet can and will lose individual outcomes; the case for it is that repeating similar bets is profitable on average.
BallBet expresses its model's edge as the gap between its projected probability and the market's implied probability. A positive edge is a positive-expected-value signal — not a prediction that a specific bet wins.
Positive expected value means a bet's price is better than its true probability warrants, so repeating similar bets is profitable on average. It describes the long run and does not guarantee any single bet wins.