This talk is aimed at people new to ArcGIS and interested in learning about the most important technologies available for creating web applications. We will start by introducing some key components of the system architecture, then we will move on to the configurable applications with WYSIWYG interfaces, then how to reuse code through low-code solutions, specifications for reusing 2D and 3D maps, a language that allows you to create dynamic content between applications, and web components. We will also explore the JavaScript libraries available to develop custom applications including the fully featured ArcGIS Maps SDK for JavaScript as well as open source libraries. Finally, ready-to-use location services and some patterns to extend and create your own.