What is a present perfect and past perfect tense?

Here is an example of present perfect: "My brother has just left for school."

Here is an example of past perfect: "I'd been to Disney Land when I was little."

The present perfect of any verb is composed of two elements : the appropriate form of the auxiliary verb to have (present tense), plus the past participle of the main verb. The past participle of a regular verb is base+ed, e. g. played, arrived, looked. For irregular verbs, see the Table of irregular verbs in the section called 'Verbs'.

The past perfect refers to a time earlier than before now. It is used to make it clear that one event happened before another in the past. It does not matter which event is mentioned first - the tense makes it clear which one happened first.

First part: John had gone out - - 2nd: when I arrived in the office.