Return on Ad Spend (ROAS) is a marketing metric that measures the effectiveness of a digital advertising campaign. It is calculated by dividing the revenue generated from an advertising campaign by the cost of that campaign. ROAS helps businesses evaluate which methods are working and how they can improve future advertising efforts. A high ROAS indicates a successful campaign generating significant revenue for each dollar spent, while a low ROAS suggests a need for optimization. This metric is crucial for businesses to ensure that their advertising budget is being used effectively, ultimately contributing to the overall profitability of their marketing efforts.