The document discusses different types of online systems and platforms. It describes social media, search engines, communication services, payment systems, advertising platforms, and creative content outlets. It also mentions various online platforms and applications for tools like presentation, photo uploading and hosting, photo editing, cloud computing, newsletters, mapping, music production, surveys, publishing projects and contents, content management, curating, web design, and web management. It concludes by defining a platform as something that can be programmed.