Java Shape Quiz

Question

Can anyone elaborate on the following line of code from the "Java Shapes Project" (in More On Classes):
Square a = new Square(x);
Circle b = new Circle(y);
Specifically, I'm not understanding the "Square a" and "Circle b" parts???
Is it just assigning "Square(int x)" to "a" ? So when it's called later in "a.area()".
If so, couldn't someone write "Circle a = new Circle(x);"
How would it know if "a.area()" was for the Circle or Square???

Answer 1

Square a = new Square(x);
it creates object of type Square and its constructor can use value of x
then this new Object is assigned to variable a of type Square
q2: no, if type of a is declared yet
q3: because a has only one type, it is not problem