What are the function perfect tenses

Perfect tenses serves a portraying the verb or the action word as something that already happened or is completed, thus the term ‘perfect’. If it is present perfect tense, it means that the action was already done relatively to the present (has/have with past participle). If it is past perfect tense, action is already finished relatively to the past (had with past participle and if it is future perfect tense, action is complete relatively to the future (will have with past participle).