There are many different modules available in Drupal that help provide e-commerce solutions for websites.
Below are examples of a few of the best modules to help with the functionality of a Drupal e-commerce site:
Commerce Guys just released a new version of Drupal Commerce— Drupal Commerce 1.0. The new version of the e-commerce platform is compatible with Drupal 7 and features product content management, order management, payment processing, personalization and product search. Other aspects of this module include the ability to create product types with custom attributes, dynamic product displays and the availability of discount pricing rules.
Ubercart focuses on three categories: store configuration, product and catalog creation and order administration. This module has many customizable options and features single page checkout, automatic account generation and simple order creation and editing. Additionally, it has the ability to fully integrate your store with the rest of your site and can be enhanced with other modules and themes. It’s a great solution for stores that sell physical goods, digital product downloads and site memberships.
The Amazon Store module is desirable for anyone selling through Amazon. After installation and activation, the user must sign up for an Associate ID— in order to receive commissions based on purchases made through your store. This module allows for searching, provides product pages and manages a shopping cart.