This document discusses how Composer can be used to manage dependencies and autoloading in Magento 1.x and Magento 2 projects. It explains how Composer works, including the composer.json file, vendor directories, and version control. It also covers how Magento 1.x and 2 leverage Composer differently, with Magento 2 fully supporting Composer and PSR-4 autoloading for modules, themes, and locales.