Difference between “var” and “dynamic” type in Dart?

Question

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

Answer 1

var a ;
a = 123;
print(a is int);
print(a);
a = 'hal';
print(a is String);

When defined without initial value, var is dynamic

var b = 321;
print(b is int);
print(b);
//b = 'hal'; //error
print(b is String);

When defined with initial value, var is int in this case.