I'll try to explain...It's Future Perfect in the Past. It is mainly used in subordinate clauses. It means an action that will be finished by a certain moment in the future. But the point is that the main clause (statement itself) already relates to the past. For example: "He said that the article would have been translated by 6 o’clock" vs "He says that the article will be translated by 6 o'clock"

''Would have been'' is used to re-imagine the past. In reality, you're saying this did not happen at all. (Or at the very least, you're not sure.) ''I was in the school basketball team.'' This is a past event, and a fact. ''I would have been in the school basketball team (if I hadn't broken my leg that year).'' You're just imagining it; it never happened. You'll see this pattern used in Third Conditional.