Can someone please explain this to me?

I read that if you think of the person of the same sex of you that you hate the most and why you hate that person can represent your shadow. I don't see this as being wholly true.

What I am really interested in is the animus in a female, and what is possession by the animus part? I'm reading a book but would love to have a synopsis as I find it curious. It talks about how the only way to know this part is by projection. I want to know what this means, maybe give an example if you know.

Thanks!