Flutter is an opensource UI toolkit from google for crafting beautiful, natively complied application for desktop, web and mobile from a single codebase. Flutter use dart as a programing.
What is Dart and What Flutter use dart ?
Dart is object oriented , garbage collected programing language from google, having inside and out community. Dart is used for writing flutter. Flutter uses dart for the following reasons.
1) Dart is AOT (ahead of time) complied for fast, predictable and native code which allows most of the flutter is written in dart. This not only allows flutter to be fast but almost everything (including all widgets) can be customizable in flutter.
2) Dart can be also JIT(just in time) complied, for exceptionally fast development cycle and game-changing workflow (eg hot reload feature).
3) Dart doesn't required an seperate declarative layout language like XML or JSX.
How is Flutter different from webview applications ?
To answer this question simple, your code in webview go throught multiple layer before finally getting executed , while flutter leapfrogs by compling the code in native ARM code that run on both of the platform. "Hybrid" apps are slow, sluggish and looks different that of platform. Moreover, native device components and sensors can he easily access and used using flutter plugins while webview don't take full use of it.