What makes you think were the author's intended audience, exactly? It sounds like the author intended their article for people who know what an IV is. You don't, and, while there's no shame in that, it does seem to indicate that you're not in the audience.

This is like me complaining that I can't understand Terry Tao's blog when it's posted to HN. It's not written for me.

You were probably not the intended audience then. It seems to me that this is intended for people who have some form of knowledge about cryptography already.

In any case, there are many articles about IVs and how to use them already so I do not see the point of explaining what an IV is yet again in that article.