The simple past tense indicates that an activity or situation began and ended at a particular time in the past.
The present perfect expresses the idea that something happened (or never happened) before now, at an unspecified time in the past.The exact time it happened is not important. It also expresses the repetition of an activity before now. The exact time of each repetition is not important.
Even though I understand the explanation above, I can't figure out: If the present perfect states the idea that something happened in the past, why not use the simple past?
For example, would you please explain the following sentence to tell the difference between these two tenses?
The plane crashed there.
The plane has crashed there.
What is the biggest difference between them?