Any verb using "have" or "has" as its auxiliary verb is in the present perfect tense.
has walked
have walked
has taught
have taught
has gone
have gone
etc.
Any verb using "had" as its auxiliary verb is in the past perfect tense.
had walked
had taught
had gone
etc.
The same can be said for the verb "to have" --
She has had two sandwiches for lunch each day this week.
They have had this television service for two years.
If he had had a sandwich for lunch, he wouldn't be hungry now.
When do I use had have had has had had
2 answers
http://www.englishpage.com/verbpage/presentperfect.html = present perfect
http://www.englishpage.com/verbpage/pastperfect.html = past perfect
Check out the other tenses in the list at the left.
http://www.englishpage.com/verbpage/pastperfect.html = past perfect
Check out the other tenses in the list at the left.