One of the modules that implements an eCommerce framework and ecosystem is the Drupal Commerce module.
The Drupal Commerce module is an eCommerce framework built on Drupal. The project started with Drupal 7, and it encompasses a strict set of core modules and works with essential contributed modules (Views, Rules, Tokens, etc). There are also a number of Drupal Distributions that combine contributed modules to satisfy particular eCommerce needs (shipping products, selling digital downloads, selling digital access, donations, etc).
The project's website contains information on the project's goals and architecture and is the primary repository for developer and administrator documentation. However, downloads and issue tracking are still handled on drupal.org through the Drupal Commerce project page.