We use this tense to show that an action happened in the past. It is an experience that a person had. They have the knowledge, experience and memories of the action today. It happened in the past, sometime in the person's life. It is not important when it happened.

For example: Mariam is 21 years old.

"Mariam, have you ever been to Africa?"  (Q)      "Yes, I have been to Egypt."   (A)

At some time in Mariam's life, she went to Africa. We don't know when and it is not important.

We do know that she has the experience and memories today of that trip she took sometime in the past.

The question uses the word "ever". We often use this to ask at "anytime in your life, have you been to ...?"

For example: "Zainab, have you ever taken a computer class?" (Q) "Yes, I have." (A)

So, today, in the present, Zainab can use a computer because she took a class sometime in the past.

We also use the present perfect to show an action that began in the past and continues into the present.

For example: "How long have you been a student at HCT? " (Q)

Answer one: "For two years."

                                            "For" tells us the amount of time.

Answer two: "Since 1999."   

                                            "Since"   Tells the exact time the action began in the past.

So... I have been a student for two years, and I still am a student. It began in the past, and it is still true today in the present.       

The simple past is used to show that an action started and finished in the past.

It is usually followed by a time or date of when the action happened.

So, we use the simple past when we know when something happened in the past.  This gives specific information.

For example: "When did you go to Egypt?" (Q) "I went to Egypt two years ago."