Short version: Attribution is the process of assigning credit for a conversion or key action to the marketing touchpoints that helped create it.
A customer may see a social ad, click a search result, read a case study, return through an email, and only then submit a form or buy. Attribution tries to answer how much influence each interaction had along that conversion path. The answer depends on the attribution model, the available data, privacy limitations, and how the business defines the conversion.
Last-click attribution is simple because it gives all credit to the final touchpoint, but it can hide earlier influence. Data-driven or multi-touch approaches can give a more balanced view where enough data exists. Attribution should guide decisions, not pretend to be perfect; it is most useful when combined with experiments, channel context, and actual revenue quality.
Related terms: conversion path, conversion rate, and campaign objective.