1. Present Perfect Tense is used for describing a past action’s effect on the present: He has arrived. Now he is here. This holds true for events that have just been secluded as well as for events that have not yet occurred.


Present perfect is formed by combining have/has with the main verb’s past participle form:
I have arrived.

A negation is produced by inserting not after have/has:
I have not arrived.

Questions in present perfect are formulated by starting a sentence with have/has:
Has she arrived?

2. Past Perfect Tense is a kind of tense that is used to describe an action or an event that started in a certain time in the past and completed or finished till certain time in the past too; or past perfect tense is used to express an action or an event that had happened before the other event or action happened

(+) We had eaten before they came
(-) They had not eaten before we came
(?) Had they eaten before we came?