Has had / have had

[Litnax]

'has had/ have had/ had had'

A couple of years ago I thought I finally understood how and when to use present perfect and past perfect tense until someone corrected me. Can some provide a simple explanation for me? I know when to use has/have/had except when to put 'had' after the verb(s)?  :confused: At this point, I only understand that we use these tenses to indicate an action that began at some point in the past and has not yet reached its end.

[OddVisions]

Has is used in refference to a singular object. For instance, Lee has been gone a while. Meanwhile, had is used in refference to plural objects. Lily and George had a good summer. Then of course there are times when had is used in referrence to the object's self. For example: I had it!