1. The present perfect tense describes an action that started in the past and continues to the present time. Use has/have + the past participle form of the verb. EX : I have run several marathons this year.
2. The past perfect tense describes an action that started and ended in the past. Use had + the past participle form of the verb. EX : I had run many marathons in the past.
3. The future perfect tense describes future actions that will occur before some other action. Use will have + the past participle form of the verb. EX : I will have run a marathon by the time I turn 30.