A value bet is one where your estimated chance of an outcome is higher than the implied probability in the book's price. Put simply, the market thinks the outcome is less likely than you do, so the odds on offer are too generous.
Value, not winners
The crucial idea is that value is about price, not certainty. A heavy favorite at stingy odds can be a bad bet, and an underdog can be a good one. What matters is whether the odds overpay relative to the true probability. A value bettor expects to lose plenty of individual bets and still profit over time, because each bet is taken at a price better than the real chance warrants.
Where the edge has to clear
Because book odds carry an overround, a bet only has value once your probability beats the implied probability including the vig. That surviving gap is the model edge. Smashrs surfaces a pick when the model's probability clears the market price by enough, and whether that approach actually profits is measured transparently in the backtest track record.
This is educational material on how prediction-market pricing works, not betting advice.