To establish the difference between the use of ‘has/have’ and that of ‘had’, one needs to understand the essence of the past perfect tense. When two things occurred in the past, the past perfect tense ...

You use the perfect tense when, in English, you would say that something has happened. So, if you wanted to say: ‘You have been to the hairdresser,' 'she has eaten all the biscuits’ or anything else ...