What is a "looking into" resistance? I'm studying transistor circuits at the moment and my textbook has mentioned the "resistance" looking into one of the terminals several times. Also mentioned is the resistance "seen" by a component. I've seen this in previous textbooks (especially with Thevenin) as well but just ignored it since it seemed I could do without it, but now it's just gotten to be too annoying. They never explain what it means and just pop it in out of nowhere and it's difficult to understand (at least for me) from the context. I also searched the Internet but surprisingly there isn't a thing.