First of all, most questions on the "difference" make no sense. How would you define the "difference"? If you did not get it, please tell us: what's the difference between apple and Apple?
You should just learn how interfaces work and how base classes work. In essence, to be honest, you need learn how OOP works, because the question is at the very heart of OOP, so just answering it exactly would be pretty pointless. Just learn both things separately, make sure you understand the use both approached, and then ask further questions, if you have to.
As to the MSDN article you referenced, you should understand that, even though MSDN documentation became very good these days, some articles are quite misleading or incomplete, and some areas are not covered at all. Unfortunately, it happens to the topics which are supposed to cover first principle, something related to fundamental notions of computer sciences. So, my advice is simple: do yourself a favor and completely disregard this short and not informative article, in particular, the sentence you quoted in bold. It's almost gibberish, honestly. Let's just forget about it.
To be useful, your question should be different: not "what's the difference"? but something like: "how to decide where to use abstract classes and hierarchy of derived classes and where the interfaces, and where to combine these approaches?" That would make the question sensible, but not trivial, and, unfortunately, not so simple. Please see my past answers:
Doubts on Interfaces[
^], actually, this answer references all other answers:
How to decide to choose Abstract class or an Interface[
^],
Difference between abstract class and interface if they have same no of methods and var[
^],
When we use abstract and when we use interface...?[
^],
Interfaces and Polymorphism[
^].
—SA
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