Data abstraction is a mechanism of retrieving the essential details without dealing with background details.
In real world we have three levels of abstractions. They are physical level abstraction, conceptual/logical level abstraction and view level abstraction.
Physical level abstraction is one; it always deals with physical organization architecture of the application. For example, in real world an application designing of any problem comes under physical level abstraction.
Conceptual/logical level abstraction is one it always deals with what kind of data we are entering without dealing with physical architecture of the application. For example, entering the data into the database, writing the coding and applying testing principle comes under conceptual level abstraction.
View level abstraction deals with what kind of data we are retrieving without dealing with both conceptual level abstraction and physical level abstraction. For example, retrieving the data from the data base in various combinations. All internet users come under view level abstraction.