I believe that, the present perfect is used when the action took place in the past; but has some connection with the present time. In this case, there's no specification of the exact time of action. Furthermore, there's an implied lenght of the action that took place. eg: I've walked down the street to welcome my parents. in this example, you note that the action expressed by the verb here is a like process. whereas, the simple past is treferred to as precise-time-oriented tense. that's, it's used when the action takes place at a specific and specified moment in the past. in this other case, we don't note (almost) any lenght in the action. eg: I went to Africa in 2012. Hence, the difference between the two tenses is much more at the level of time, action duration and its connection to the present time. now, consider the following sentences: 1.I went to Africa in 2012 2.I have gone in Africa in 2012*(do you see how odd is this one?)

I believe that, the present perfect is used when the action took place in the past; but has some connection with the present time. 

In this case, there's no specification of the exact time of action. Furthermore, there's an implied lenght of the action that took place.

I've walked down the street to welcome my parents.

In this example, you note that the action expressed by the verb here is like a process. Whereas, the simple past is preferred to as precise-time-oriented tense. i.e., it's used when the action takes place at a specific and specified moment in the past.

In this other case, we don't note (almost) any length in the action.

I went to Africa in 2012.

Hence, the difference between the two tenses is much more at the level of time, action duration and its connection to the present time. now, consider the following sentences:

1. I went to Africa in 2012.
2. I have gone in Africa in 2012*.

(Do you see how odd the second one is?)