This document discusses online platforms and systems. It begins by defining a platform as a website that allows users to create and program web content remotely. It then discusses how online platforms bring together consumers and producers. Examples of major online platforms are provided, ranging from search engines and marketplaces to social networks and video sharing sites. Potential dangers of being online like phishing, viruses, and hacking are outlined, along with tips for safe internet use such as using strong passwords, VPNs, and anonymous browsers. Guidelines for ethical online behavior called "netiquette" are also summarized.