abstract and interface class

eatures                                      Interfaces                                abstract class

Multiple inheritance	A class may inherit several interfaces.	A class may inherit only one abstract class.
Default implementation	An interface cannot provide any code, just the signature.	An abstract class can provide complete, default code and/or just the details that have to be overridden.
Access Modfiers	An interface cannot have access modifiers for the subs, functions, properties etc everything is assumed as public	An abstract class can contain access modifiers for the subs, functions, properties
Core VS Peripheral	Interfaces are used to define the peripheral abilities of a class. In other words both Human and Vehicle can inherit from a IMovable interface.	An abstract class defines the core identity of a class and there it is used for objects of the same type.
Homogeneity	If various implementations only share method signatures then it is better to use Interfaces.	If various implementations are of the same kind and use common behaviour or status then abstract class is better to use.
Speed	Requires more time to find the actual method in the corresponding classes.	Fast

Regards,
Praveen Nelge

Well, first of all you can't create an object of either an abstract class or an interface.

What you can do is to:

1. Declare a variable or parameter of the abstract class's type. This variable can then contain a reference to any object which inherits from the abstract class.

2. Declare a variable or parameter of the interface's type. This variable can then contain a reference to any object which implements the interface.

This allows you to write generic code which applies to any class derived from the abstract class or any class which implements the interface.

Normally, there is no relation between classes which implement an interface except for the common functionality which it represents. However, there usually is a relationship between an abstract base class and its derivatives.

A class can implement any number of interfaces but can only inherit from a single class (abstract or not).

For more on the differences between the two, check the links below your post.