Hello.

There is no clear difference from this description. At least not me (I'm new to UML). An abstract class works on top of other classes without knowing the details of the implementation (eg a class that can sort any field if the operator <is defined) - i. an abstract class can contain an abstract code. (?)

There is only a definition of an interface that some interfaces exist (i.e. a class implementing these functions can use these functions in its calculation) but there must be another class that implements the given functions. E.g. object for archiving other objects.

What are the typical examples of using an abstract class and interface?

It is not yet clear from the figure when the interface with the ball is used in the interface and when with "C". and how to draw some interfaces in the example (the picture only shows the elements that will be used.

(The text has been machine-translated.)