Ionic is a mobile app development framework used to build hybrid apps. Hybrid apps are basically web apps running in a browser within a wrapper that  has access to the native platform layer. Ionic framework is an HTML5 framework. It needs a native wrapper like Cordova or PhoneGap in order to run as a native app. Ionic framework lets you maintain one codebase and create builds for both Android and iOS platforms. NodeJS , npm are required in order to install Ionic. You need NodeJS 6.0.0+ or a higher version in order to install ionic.