Perfect is the name given to those forms of the verb constructed with HAVE and the Past participle (Third form) of the verb. These forms are often known as tenses, though many modern writers prefer to consider them as aspects; The four perfect aspect forms, with examples, are:
1. The Present Perfect: I have worked, you have gone
2. The Present Perfect Progressive (or: Present Perfect Continuous): he has been working, they have been going
3. The Past Perfect: we had worked, she had been working
4. The Past Perfect Progressive (or: Past Perfect Continuous): you had worked, I had been going.
Some writers call #1 the Present Perfect Simple and #3 the Past Perfect Simple, but most prefer to use 'Simple' only for tenses that are both non-progressive and non-perfect, i.e the Present Simple and Past Simple.