What is a widget ? Mention its importance in Flutter.

A widget in Flutter is a fundamental building block that describes part of the user interface. Widgets are the core concept in Flutter's framework and are used to create beautiful, responsive, and dynamic mobile apps[1][2].

Widgets are important in Flutter for several reasons:

1. Widgets are the basic visual elements used to create user interfaces and define an app's functionality[1].

2. Widgets can be combined and arranged in many different ways to create complex user interfaces, similar to Lego blocks[1].

3. Widgets form a hierarchy based on composition, where each widget nests inside its parent and can receive context from the parent[2].

4. Apps update their user interface in response to events by telling the framework to replace a widget in the hierarchy with another widget[2].

5. **Flutter has its own implementat...