Grammar

Past Perfect Tense
Grammar Essential #93
Past Perfect definition
As a verb form, the most common use of the past participle is to form what are known as the perfect tenses (they are called "perfect" because they refer to actions that have been or will be completed).

Past perfects are made by using
the imperfect tense of haber +
past participle
Present perfect
In English, the perfect tenses are those formed by using a form of the auxiliary verb "to have" and following it with the past participle; in Spanish, they`re formed by using:
haber conjugated ("to have") + past participle.

Just like in present progressive is estar + present participle.
Present Perfect
It may come as no surprise that the verb is haber, which is translated as the auxiliary verb "to have." As an auxiliary verb, haber in Spanish and "to have" in English are used to form the perfect tenses.
Past Perfect - Haber
Haber = to have (as an auxiliary)

Is not used alone. It is a helping verb.
Making past perfect
Make the past perfect by
haber (conjugated)+ past participle.
I had seen.
Yo había visto.
You (s. fam.) had won.
Tú habías ganado.