The conjunctions we have seen so far introduce a subordinate clause that describes an event / action with a temporal, final, causal, concessive, conditional relationship to the action / event described in the main clause. In the case of conjunções aditivas we don't have any relationship. One sentence is just added to the other and we can even change the order without changing the meaning. (Something never possible with subordinate clauses.)
In the morning he goes to work and in the evening to the university.
In the evening he goes to the university and in the morning he goes to work.
He sleeps or he does nonsens.
He does nonsense or he sleeps.
He is as rich as greedy.
He is as greedy as rich.
This is not possible with subordinate clauses.
1) He is hungry although he have just eaten.
2) He has just eaten, although he is hungry.
2) is for obvious reasons nonsense.
In opposite to the conjunctions we have seen so far the copulative conjunctions can connect adjective, "He is mad and ill", nouns, "I don't like either beer nor wine", adverbs "He laughs loud and often". This author would say that these conjunction are completely different type of words.