---
title: Mapping
slug: '217'
canonical_url: https://docs.coveo.com/en/217/
collection: glossary
source_format: adoc
---
# Mapping
A {doctitle} is a rule that defines which piece of [metadata](https://docs.coveo.com/en/218/) a [source](https://docs.coveo.com/en/246/) should [index](https://docs.coveo.com/en/204/) in a  [field](https://docs.coveo.com/en/200/) when an [item](https://docs.coveo.com/en/210/) passes through the [Coveo indexing pipeline](https://docs.coveo.com/en/184/).