'All' is usually used as a determiner, which means that it is part of a noun phrase, for example 'all the time' or 'all my friends' . This corresponds to the Spanish form todo/toda/todos/todas: 'all the books' = 'todos los libros' 'Everything' is a pronoun, which means that it can stand alone. 'Everything' can be the subject or object of a sentence. This corresponds to invariable Spanish form 'todo'. 'Quiero comprar todo' = 'I want to buy everything'. He ate all the food on his plate. = He ate everything on his plate. We put all our bags in the car = We put everything in the car. I like all the music which John plays = I like everything that John plays. You can't say, for example 'He ate all on his plate', because 'all' can't stand alone in this way. We have to know 'all of what?'. 'Everybody/everyone' and 'everywhere' work in the same way. All the students passed the exam = Everybody passed the exam I hope that helps.

They are interchangeable in most cases, but sometimes you can only use one of them even though they both mean the same thing. For example Do you like what you see? Yes, I like it all. or What would you like? I would like everything. I am sure there are some grammatical rules which apply, but it is probably better to work on the flow of the words, rather than getting bogged down in grammar.