eBay is an online marketplace where companies and individuals can sell new and used items, or bid against each other on buying those items.
Volusion is an eCommerce hosting platform that allows users to create a store and start selling online.
3dcart is an eCommerce platform for creating a successful online store. They put an emphasis on search engine optimization.
BigCommerce is an ecommerce platform that specializes in a variety of use cases and industries.