Different terms used to refer to the same thing

Dear teachers:

According to this page https://dictionary.cambridge.org/us/grammar/british-grammar/complements, there are five major elements of a clause structure: Subject, Verb, Object, Complement, and Adjunct.

But I've learnt that "Objects" are a type of "Complements", i.e., just the term "Complements" can be used to refer to "Objects". I have got somewhat confused now. Is there something that I'm missing here? Do they (Objects and Complements) refer to two different grammatical functions?

Another question I have is that is there any difference between "Modifiers" and "Adjuncts"? Or they are just two different terms to refer to the same thing?

Thank you!