There are three major categories of mobile apps, ‘Native apps‘, ‘Hybrid apps‘ and ‘Cross Platform apps‘.
Native Apps-
Platform specific technologies like Cocoa Touch library, Objective C/Swift language are used for iOS and Android APIs, Java language are used for Android. These types of apps are having highest performance and smallest footprint. But knowledge needed for each platform to develop an app and there is no code sharing.
Hybrid Apps-
These apps are deployed in an app store but are actually web apps developed using plain HTML, CSS and JavaScript. Code and UI are reusable across platforms and JavaScript libraries can be used like JQuery, AngularJS, ReactJS or Knockout etc. There are number of tools available to develop a hybrid app like Apache Cordova, PhoneGap, Telerik AppBuilder and Ionic (based on AngularJS).
Cross Platform apps-
These apps are developed using a framework which enables the sharing of code between mobile platforms. One programming language is used for all platforms but mobile platform knowledge is required. There are many products available like – Xamarin (C# is used and you can use same UI code or can create different for each platform), Titanium (JavaScript is used and converted to native by JavaScript interpreter), React Native (JavaScript is used and based on React framework), NativeScript (Angular, TypeScript or JavaScript is used).