Inferring the type

Dart is a typed language. The type of the variable message is String. Dart can infer this type, so you did't have to explicitly define it as a String. Importantly, this variable must be a String forever. You cannot re-assign the variable as an integer. If you did want to create a variable that's more dynamic, you'd use the dynamic keyword. We'll see examples of that in a later lesson.

dynamic message = 'Hello World';

You can safely re-assign this variable to an integer.

dynamic message = 'Hello, World';
message = 8; 

NB: It's rarely advisable to use dynamic. Your code will benefit from being type safe.