Probability of profit is the model-implied chance that a position finishes profitable at expiration, computed from the chain's own implied volatilities via N(d2) at the breakeven. It states odds under the market's distribution, not a promise, and ignores the size of wins and losses.
Probability of profit asks one question: under the distribution the options market is pricing, how likely is this position to finish expiration above (or below) its breakeven? It is a property of the trade's structure and the chain's implied volatility, not a forecast of the stock.
A bull put credit spread on a $100 stock, 30 days out, sells the 95 put and buys the 90 put for a $1.00 credit. The breakeven is $94. At a flat 30% implied volatility, the model's chance of the stock finishing above $94 is about 76 percent. That is the spread's POP.
Careful implementations evaluate POP at the breakeven with that strike's own implied volatility rather than the at-the-money number, and correct for the slope of the volatility smile. The number is only as good as its calibration: grouping closed trades by entry POP and comparing forecast odds with realized outcomes is the audit that keeps it honest. The full mechanics are in the probability of profit article, the app's exact method is in the POP methodology, and the POP calculator runs the number for any strikes.
The model-implied chance that a position finishes expiration with any profit, measured at its breakeven using the chain's implied volatility. It describes the distribution the market is pricing, not where the stock will go.
Not by itself. POP says nothing about the size of wins and losses: a credit spread with a 76 percent POP might make $100 and lose $400, so the odds and the payout have to be read together.
Delta approximates the chance of an option finishing in the money at its strike; POP measures the chance of the whole position finishing beyond its breakeven, which includes the premium collected or paid.