Implied odds
The extra money a drawing hand expects to win on later streets if it hits, added on top of what raw pot odds alone justify.
Implied odds are a refinement on pot odds, not a substitute for them. A call that loses on the raw pot-odds comparison can still be correct once the money likely to be won later, when the draw completes and gets paid, is added to the pot it is being priced against. The reverse also matters: a hand that is easy to play after it hits carries more implied odds than one that is obvious and gets little action, so master the raw pot-odds comparison first and treat implied odds as an adjustment on top.