Some questions about inheritance

Hello Experts!

I have some questions about inheritance that I want to have an answer to.

It says "Abstract superclasses define a behavioral pattern without
specifying the implementation"
I know that an abstract class doesn't have any implementaion even if a
default implementatiion can be supplied for pure virtual methods.
What does it actually mean with saying that an Abstract superclasses define
a behavioral pattern?

What does it mean with saying that subclasses should respect the semantics
of the superclass?

Code inheritance
This form of inheritance could be called "convenience inheritance". The
subclass "is not a" superclass,
but can use some of its implementation. The functions of the superclass need
not be valid for the subclass, and if they are they may have different
semantics.
Here what does it mean with saying . . .and if they are they may have
different semantics?

Is delegation the same as aggregation and composition?

Many thanks

//Tony



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