Magento Open Source, formerly known as Magento Community Edition, is the free version of Magento. As it's open-source, this means it is freely available for download and modification. While this version provides many basic e-commerce features, the lack of some advanced functionalities could be a limitation for larger businesses. Magento Commerce, formerly known as Magento Enterprise Edition, is the paid version of Magento. It includes all features of Magento Open Source, but adds a number of powerful extras, including enhanced security features, extensive analytics, improved performance and scalability, and professional support. This version is designed for larger businesses that require a robust and comprehensive e-commerce platform. So, in summary, the biggest differences between Magento Open Source and Magento Commerce lie in the features, scalability, support, and price. The choice between the two depends on your business's needs and budget.