In Interface,we cannot specify any definition inside but
where as class we can.

interface is define as the declaration part of the function.
interface is differ from the class by class can access the 
interface but interface cannot access the class

Class can hold both member function and data, depending upon
the member function class becomes abstract class and etc.
but if a class contain only pure virtual function then it
becomes "Interface",remember all functions should be pure
having no data member.

interface is collection of abstract method.we can not 
define any method in interface.we can implement that 
abstract method by using the class.there is a restriction 
in interface that you have to implement  all the abstract 
method in the class which is declared in interface.and we 
can not create an object of interface.if we want to execute 
the interface method then we have to implement first that 
interface in any class after that create the object of 
class ,then we can access execute that method


but in class we have to define the methods, which is 
declered.we can also access that method through the object 
of the class.