A vertical spread combines two options of the same type and expiration but different strikes - buying one and selling the other. Selling the second option offsets part of the cost of the first, which caps both your maximum loss and your maximum gain. It's the defined-risk building block of options strategy.

Debit vs credit

A debit spread costs money upfront (you buy the more expensive option) and profits if the underlying moves your way. A credit spread pays you upfront (you sell the more expensive option) and profits if the underlying stays put or moves away from the short strike. Debit = directional bet; credit = a bet on where price won't go.

The trade-off

Versus buying a single option, a spread is cheaper and reduces vega and theta exposure - the sold option offsets some decay. The cost is capped upside: you can't catch a runaway move because the short strike caps your gain. You trade unlimited potential for a cheaper, more probable, defined-risk position.

A spread trades the dream of a home run for the reliability of a defined-risk single.

Where it fits

Spreads shine when you have a directional view but want to reduce cost and volatility exposure, or when you want to define risk precisely. They're more complex to manage than a single long option and involve two sets of fills and slippage. Powerful in the right hands - and one reason to understand the mechanics before layering strikes together.