Nice start stvn!

Here are my observations and questions about this draft, since you asked :)

General Comments

• Who is your audience, and what is their assumed level of knowledge and experience?

• It might be useful to have some introductory text that gives your subject a context and establishes some clearer boundaries

• There are many other sources of introductory information available on the WWW, perhaps you could link to, or quote from some of these to a) provide a foundation and context for your writing and b) provide further reading where your treatment is deliberately light and c) support your definitions

• When you make assertions such as

  greatly misunderstood

  it would help the reader if you also give an example of how the subject is misunderstood, otherwise how is the reader to know what the wrong understanding actually is, so they can avoid it themselves

Specific Comments

• You explain the IS-A and HAS-A relationships, but in your example of multiple inheritance you also mention a LIKE-A relationship:

  A Platypus is-a Mammal but it also lays eggs like a Bird.

  This could be confusing since LIKE-A has no further explanation or comparison in your text.

• Is it really necessary to try and explain mix-ins? Frankly I've not heard of them before (not that I'm a good yardstick), but it sounds like they are an unwelcome hybrid based to some extent on an abuse of language features. If it is true that they do

  tend to play havoc with inheritance

  then perhaps a lesser discussion would be appropriate, maybe just a single sentence for the sake of completeness.

• I found this sentence unclear:

  A class that implements an Interfaces enters into a contract with all consumers of that class that the methods (implemented or stubs) from said interfaces will be there.

  Will be where? I think I know what you mean. Perhaps this could be re-worded like this:

  A class that implements an Interface enters into a contract with all consumers of that class that it will implement all methods declared by the Interface.

• I also found your introduction of the IS-A-TYPE-OF relationship somewhat confusing.

  Interfaces are best characterized as "is-a-type-of"

  To me this reads as though "Interface" is synonymous with "Inheritance". In contrast, I conceptualise Interfaces as a HAS-A relationship but where the details are left to the consumer of the object. To me an Interface says things like

  A car has a dashboard that shows current speed and distance travelled, but it doesn't matter (to me, the base class) what this dashboard looks like or even how it communicates these details.

Please don't take any of this as negative criticism. As I said, I think what you've written so far is a good start.

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Update: Added bullets for clarity