difference between instance & object

1) An instance refers to an existing object, where as an object is the type.

Think of it this way,
A car is the object, but the instance is the one you drive (versus the one I drive).


2) An abstract class allows an inherited class to use polymorphism (overloading). It also allows logic that all inheritted members will have.

For example a Car may be the abstract class but Sedan and Sporty will use it for a parent class. The "Car" abstract class will likely impliment the logic for MPH as it is the same regardless of whether is is a Sedan or a Sporty car.


3) Static means no instance is necessary. For example the Car abstract type referred to earlier may actually inherit Vehicle which has a property WheelCount. The Car static type would result in 4 where as MotorCycle would return 2. There is no need to have the Sedan instance track this as all instances of all Cars will have the same wheel count. So one would likely set the value of the wheel count in an abstract static Car constructor or some initialization method.

object is the class variable with memory assign to all its fields but no value set between them and instance is a object of class at run time when all fields get value assign example
public class cls
{
public string name{get;set;};
public string roll{get;set;};
}

then object represent in memory as

name point to memory

roll point to memory

and instance represent in memory as

name point to memory where value "Ganesh" is store in name

roll point to memory where value "1" is store in roll