Attribution is the method used to assign credit for a conversion or sale to marketing interactions.
How it works in retail
Rules may allocate credit to a final click, several interactions or a modelled contribution. A reporting window defines how long after an interaction a conversion can qualify.
A retail example
A shopper clicks an ad and buys three days later. Whether the campaign receives credit depends on the reporting rules and window.
What to keep in mind
Attribution records an assigned relationship. Incrementality asks whether the outcome would have happened without the marketing activity, which requires a different evaluation.
Sources & further reading
IAB/MRC: Retail Media Measurement Guidelines
Examples are illustrative. Terminology and measurement conventions can vary by business and market.