What are Flutter animations and how to implement them?

Flutter animation system:\n\n**Animation types:**\n• Implicit animations - Automatic transitions\n• Explicit animations - Manual control\n• Hero animations - Shared element transitions\n\n**Implicit animations:**\n\nAnimatedContainer(\n duration: Duration(seconds: 1),\n width: _isExpanded ? 200 : 100,\n height: _isExpanded ? 200 : 100,\n color: _isExpanded ? Colors.blue : Colors.red\n)\n\n\n**Explicit animations:**\n\nclass _MyWidgetState extends State \n with SingleTickerProviderStateMixin {\n AnimationController _controller;\n Animation _animation;\n \n @override\n void initState() {\n _controller = AnimationController(\n duration: Duration(seconds: 2),\n vsync: this\n );\n _animation = Tween(\n begin: 0.0,\n end: 1.0\n ).animate(_controller);\n }\n}\n\n\n**Common animated widgets:**\n• AnimatedOpacity, AnimatedPositioned\n• AnimatedBuilder, FadeTransition\n• SlideTransition, ScaleTransition