If you want to know what is a variable you can click here, in this brief explanation i will suppose that you have a little knowledge about variables and how they work!

Dart variables even if they are strongly typed you can omit the type since it's optional. You can change the type in time by just adding it before the variable, after the declaration when needed, So you can write:

var a = 'test';
String a = 'test'; 

You can define private variables by adding a underscore sign before the name, for example:

var a = 'Private variable';

When you define variables without any value they get initialized with "null" (numbers too). Like javascript everything inside variables are Objects.

List of types:

The list of the types that you can use are:

• String
• Boolean
• Number (int or float)
• List (array)
• Sets
• Maps
• Runes
• Symbols

As said before if you want to define a variable without typing manually the type you just have to declare the variable by using the "var" keyword.

When you know that you variable will ever change it's value you can use either "final" or "const"