what's oxidation?

Had an enjoyable chat with tea people on Google+ Hangout the other night. There was discussion about Oolong that I won't even attempt to go into here, but one of the things I was curious about was how the others explained what Oolong was to people new to tea.

That's a fair question, right? I get it all the time.

People know black tea and green tea, but mention of Oolong leaves many people looking a bit befuddled.
So how to explain it?

And as you know, I'm normally looking for the most concise description. That's ridiculous of me to even say, isn't it? Would I really be looking for the most intricate and detailed description? Not here I wouldn't.

Simply put, green tea is not oxidised and black tea is fully-oxidised. Oolong falls somewhere in the middle between the two. Some Oolong is lightly oxidised, some is allowed to oxidise much more but not fully. Next question for someone who's curious and whose eyes haven't glazed over already:

Uh...what's oxidation?

Well, here's an article you probably won't even bother clicking over to: Oxidation & Fermentation in Tea Manufacture

And the article uses the same very simple example of oxidation that the above-mentioned tea people did. If you cut an apple in half and let it go brown, that's exactly the same chemical process that tea goes through when it oxidises.

The specifics of the process of letting tea oxidise is certainly very complicated and the most sought after Oolong was very likely tended by a highly experienced tea master.

Although this is rather basic information when it comes to tea, I am asked this question often. Do you have any other ways that you explain oxidation? I'd love to hear them.