What is the main role and application of the keyword final in programming?

In the Dart language, used in Flutter, the keyword final is used to declare a variable whose value can only be assigned once. After initialization, the value of a final variable cannot be changed.

Example:

final String name = 'Alice';
// name = 'Bob'; // Error: cannot change the value of a final variable

The difference from const is that const means a compile-time constant, while final is a runtime constant, meaning the value can be set dynamically but only once.