Marketing attribution
Marketing attribution assigns credit for pipeline or revenue to the marketing touchpoints before it, using a model such as first-touch or multi-touch.
In practice
Attribution shapes where budget goes, so disagreements about it are really disagreements about spend. Every model is a simplification; the useful part is agreeing on one, applying it consistently and knowing what it leaves out.
Pick a model for each decision: first-touch for what creates demand, last-touch for what converts it, multi-touch for the path in between. It depends on consistent campaign and source fields on every contact, so clean source data comes first.