Behavior of declared Scanner variable?

Answer 1

Scanner is an object so I will explain it in general. A declared object just allocates the memory for the real object. Because there is no real object behind a simple declaration it can not do anything.
To get an object with functions and more you have to initialize one.

Answer 2

Scanner allows you to insert input into the program in order to create dynamic program.

Answer 3

Scanner variable = new Scanner (System.in);
int price;
price. = variable.next();