In Flutter, widgets are either stateless or stateful. A StatelessWidget is a widget that does not have any mutable state, whereas a StatefulWidget is a widget that can have mutable state.

Here are some key differences between the two :

State : A StatelessWidget is immutable, which means that its properties cannot change once it is created. A StatefulWidget, on the other hand, can have mutable state, which can change over time and trigger a rebuild of the widget tree.

Rebuild : Since a StatelessWidget is immutable, it only needs to be built once, and its build method is called only once during its lifetime. A StatefulWidget, however, can be rebuilt multiple times if its state changes, and its build method can be called multiple times during its lifetime.

Performance : Since a StatelessWidget does not have any mutable state, it can be more performant than a StatefulWidget. This is because Flutter can cache the widget and its subtree and reuse it if necessary, without having to rebuild it. A StatefulWidget, on the other hand, can be less performant because it needs to be rebuilt every time its state changes.

Use cases : StatelessWidget is best used for displaying static content or content that does not change over time, such as headers, buttons, and icons. StatefulWidget is best used for displaying content that can change over time, such as user input, animations, and complex UI elements.