- The Present perfect: I have worked here for over twenty years. - You have gone
- The Present perfect progressive (or present perfect continuous): He has been working. - They have been living.
- The Past perfect: We had worked it all out. - I had spoken to him on several occasions.
- The Past perfect progressive (or past perfect continuous): I had been working all morning on that. - He had been living there until he got that new place.
Some writers call #1 the Present Perfect Simple and #3 the Past Perfect Simple, but most prefer to use the word 'Simple' only for tenses that are both non-progressive and non-perfect, i.e. the Present Simple and Past Simple.
The perfect tenses in English are used to relate two time points or periods: 1. the time at which the situation denoted occurred or began, and 2. a later time point or period. It has been suggested that 'Retrospective' would be a more appropriate name for these forms.