|Visible and Hidden aspects|
Only the name of the class and the headers (signatures) of some selected operations are visible to client classes. The data (variables) of the class should always be private.
Which aspects of a class are hidden, and which aspects are visible from outside the class?
On this illustration, the purple aspects correspond to the tip of the iceberg. Please take a careful look at it and be sure to understand the analogy.
Read more about visibility in the text book version of this material.