According to this article:
As you might know,
dynamic(as it is now called) is the stand-in type when a static type annotation is not provide
var, like final, is used to declare a variable. It is not a type at all.
Dart is smart enough to know the exact type in most situations. For example, the following two statements are equivalent:
String a = "abc"; // type of variable is String
var a = "abc"; // a simple and equivalent (and also recommended) way
// to declare a variable for string types
On the other hand, dynamic is a special type indicating it can be any type (aka class). For example, by casting an object to dynamic, you can invoke any method (assuming there is one).
(foo as dynamic).whatever(); //valid. compiler won't check if whatever() exists
(foo as var).whatever(); //illegal. var is not a type