"I am him."
Translation:Я это он.
The point I was trying to make was that, like это in this case, the "-" is used to indicate "something on this side of the dash" equals or applies to "something on the other side of the dash". As in "Он" - "брат" means, he is my brother. "Брат - медик" means, my brother is a medic.
So whenever you use это in this manner, you can substitute it with the "-". Similarly, if - like me - you keep forgetting when to use это, эта or этот (you run into this later, as A_User stated) you can just leave it off and use the "-" as your wingman. 8D
But to answer your other question, yes, there are also plenty of cases where you can just leave off the это and the "-" because it is clear enough from the sentence structure what is meant without them. It's one of the upsides of Russian, I guess? :)
Useful guide to это by olimo: https://www.duolingo.com/comment/11536858
You can probably see it like "Я" = I am, where 'to be' is implied, as it is not a verb that is used the same way in English as it is in Russian, "это он" = this he (person you are talking about).
Это in this case is used to specify the subject (object? uh.. the он) in any case. So it is "this he".
So you get: "I am this person" or "This him/this person, I am he."
For more information on the use of это, see this guide by olimo: https://www.duolingo.com/comment/11536858
It's okay if it doesn't make any sense to you right now. Repeated exposure will help your brain get used to seeing this in a certain context and slowly, it'll start making sense and you'll get it. Doesn't mean it's not frustrating when it doesn't still make any sense, but.. :)