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This post gives a detailed description of the difference between present perfect tense or simple past tense.
Present Perfect Tense:Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
When we are thinking about the past and present together.  Â
Past Simple Tense:
When we are not thinking about the present
Examples
We have studied enough to pass the exam (the exam is still to come)
My sister has learned French. (She can speak French now)
Shakespeare probably learned Italian.
Finished Time Words with Past Simple
With Finished time Words {Past Simple is used:Â Anywhere, yesterday, last week, then, ago.
Use of Past Perfect Tense
1.     It is used for the earlier past.
2.     A common use is to ‘go back for comment when we are already talking about the past, to make it clear that something had already happened at the time we are speaking about.
(Past tense)Â Â Â Â Â Â Â Â Â Â Â Â (Earlier Past)
When I arrived at the party, she had already gone home.
Structure of Present Perfect Tense:
Affirmative/Positive Sentence
Subject + Has/Have + 3rd Form of Verb + Object
Negative Sentence
Subject + Has/Have + not + 3rd Form of Verb + Object
Interrogative Sentence
Has/Have + Subject + 3rd Form of Verb + Object
WH Interrogative Sentence
WH word + Has/Have + Subject + 3rd Form of Verb + Object
Final Words
This article explains the difference between present perfect and simple past or past indefinite.
