What Is Instance Of Class?

It is an object that is created to achieve desired results even when observing encapsulation. For example:
Variables and methods cannot be referenced from a static context and so when you want to use a variable constructed and initiated outside a static method, in a static method, you have to create an instance of that class in form of an object then call the variable using the object.
Check:

public Class MyDemo
{
  String youGuy;

  public static void main (String [] args)
  {
     MyDemo theInstance = new MyDemo;
     theInstance.youGuy = "Guest, Who?";
     System.out.print (theInstance.youGuy);
  }
}

Instances can also be used when dealing with subclasses and superclasses.
I hope this helps: Sorry it's freestyle!