The Present Perfect Tense is used to describe an action that occurred in the past, but the exact time of the action is not important. It is formed using the auxiliary verb 'have' (or 'has') and the past participle of the main verb. The Present Perfect Tense can be used to describe an action that started in the past and continues up to the present, or has just been completed. It can also be used to describe a past action that has a connection to the present.