Many a times when we use certain tools, we hardly pay attention to the details about the functionality of the tool. We hardly pay attention to the various other units, which make up the tool. This behavior to ignore unwanted details of an entity is termed as abstraction.
Now if the details are unwanted why show them to the user? Therefore, the creator might attempt to hide these unwanted details. This behavior is termed as encapsulation. So we can say that encapsulation is an implementation of abstraction. Encapsulation directly leads to two main advantages:
Data Hiding: -- The user of the class does not come to know about the internals of the class. Hence, the user never comes to know about the exact data members in the class. The user interacts with the data members only through the various member functions provided by the class.
Data Security: - Since the data, members are not directly available to the user directly but are available only through the member functions a validity check can always be imposed to ensure that only valid data is been inserted into the class.
So a Date class, which contains individual data members for storing date, month and year, will have it ensured the month is never 13 or the date is never exceeding 31.