What is 'static'? What does it mean and what is it used for?

Answer 1

If you want a bunch of utility functions available throughout you app declare them as static methods in a class and you can use them whenever and wherever without having to instantiate an object of that class. Just like you use Math.sqrt as Aditya pointed out.

Answer 2

static variables and function are access without using object of class, like

Math.sqrt

sqrt is static in Math class. Without static is like

Scanner s = new Scanner(System.in);

here you have to create object on Scanner to use

s.nextLine();

function, coz nextLine() is not static.