Thank you for this clarification of 'confusing words'.

I somehow think that 'collocations' are words made from 2 or more other (usually simple) words; usually collocations mean something quite different from the meanings suggested by their component words. For examples 'stand in' (act in place of someone who is responsible for the duty); 'black sheep' (odd one out - from the rest of the group); 'red herring' (a distraction - from the main issue); and so on.

In this sense, 'slang words' are also 'collocations'.