How does ibid work in footnotes?
Context
So I'm writing an essay, using footnotes for the first time. I was told that if I use the same source twice on the same page, then I should write "ibid", but this was not very clear. I was left with multiple questions (apologies if this ends up a duplicate, it seems like the type of question which might've already been asked but I can't find it):
Question
Where does the ibid go? In the superscript in text or on the footnote? In what combination?
How is it clear what the ibid is referring to? Say I have 4 footnotes, the fourth being an ibid, how is it clear whether the ibid refers to the 1st, 2nd, or 3rd footnote?
I've seen something about putting the page number of a journal - what about for websites, and videos? How does that work?