The present perfect tense changes verbs.  If an action started in the past, and it is still happening, you should use the present perfect tense.  It is different than the simple past, because in simple past the action is finished.  Look at the examples below and I’ll show you the difference between simple past and present perfect.
Let’s look at these sentences and compare the present perfect tense to the simple past.

Simple Past          Present Perfect
1. Bob taught English.         2.  Bob has taught English for 5 years.
3. Mary lived in Prague.      4.  Mary has lived in Prague for 10 years.
5. Bill cooked dinner.          6.  Bill has cooked dinner at church for 2 years.

Sentence 1:  Bob taught English. = Bob taught English and is finished.
Sentence 2:  Bob has taught English for 5 years. = Bob started teaching 5 years ago, and he is teaching now.
Sentence 3:  Mary lived in Prague. = Mary lived in Prague, but does not now.
Sentence 4:  Mary has lived in Prague for 10 years. = Mary lived in Prague, and she still lives in Prague.
Sentence 5:  Bill cooked dinner. = Bill cooked dinner and everyone ate it.
Sentence 6:  Bill has cooked dinner at church for 2 years. = Bill cooked dinner at church for the last 2 years, and he still does.

      Do you see how the simple past shows actions that are finished, and the simple present shows actions that are still going on?  Do you also see how in the present perfect, there is also the word “has” and a time period in the sentence, i.e. 5 years, 10 years, 2 years?  The word “has” and the time period shows how long someone has been doing the action.

자료제공:  1대1 영어 과외 온라인 영어학교 English Academy