For example, a racquetball is a particular color and size, and only the ball's manufacturer can alter those characteristics. In order to change its embedded data, an object must possess a member function to manipulate the data. As a case in point, consider the racquetball example mentioned above. One characteristic of racquetballs is that the more times they bounce the less resilient or bouncy they become. Hence the bounce-height function is localized to one particular object and can only affect that object's data.
Every object belongs to a class, but no classes are objects.
In the previous example, the racquetball object belongs to a class called Ball. If your program has a section for simulation the bouncing of a ball, it can bounce a blurp as well as any other Ball object because the mechanism that defines how to bounce a ball in incorporated into the class Ball. The class concept, therefore, means you don't need to program each ball-bouncing function separately for each type of ball. It's a ball with slightly different characteristics. All previous characteristics of a Ball are now part of Football, but the new Football class also has some characteristics that set it apart from the Ball class.