Hi, here are some modern resources.

First, what's the problem? http://www.cap-lore.com/CapTheory/ConfusedDeputy.html

What are capabilities? http://habitatchronicles.com/2017/05/what-are-capabilities/

Is there someplace with a massive pile of links? https://github.com/dckc/awesome-ocap

Yes, capabilities are abstract and simple. Don't worry if you don't get it at first.