perfect past tense preterit tense differences in usage

Question

what is the difference between pluperfect tense and past anterior/preterit usages in sentence. they both mean the had ?

Answer 1

The main difference between the two is that with the past anterior there is greater sense of immediacy between the two actions than is true of the pluperfect; however, the past anterior (pretérito anterior) is not that widely used in spoken Spanish and is often limited to literary usage.

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