WordPress is the largest content management system and currently powers more than 25% of the websites on the internet. There are an unlimited number of plugins that can help you to extend the functionality of the base WordPress installation, and one of the most commonly used types of plugins is e-commerce shopping carts, which allow WordPress sites to take orders for specific items that have been listed in a shop. There are many free plugins that can be installed with your WordPress installation, and then many offer additional add-ons that can further extend your e-commerce shop.