Hello. These two tenses are notoriously confusing. Present perfect is used to talk about something that happened from sometime in the past to the present and is completed (usually) at the time of speaking. The thing being mentioned already happened, but we don't know exactly when. For example, "I have traveled the United States." We know that the traveling occurred, we know it is finished, but we don't know when. It could have happened ten years ago or it could have happened last year. We use simple past to indicate that something happened at a very specific time in the past. For example, "I traveled the United States last summer." In this case, we know the specific time that the event happened. Also, with simple past, the exact time doesn't have to be stated. It can be implied: "I traveled the United States." Even though we didn't say "last summer," the implication is that it happened at a particular time. I hope this helps.

Use the simple past when the action started in the past, finished in the past, and is not continuing now. Use the present perfect when the action started in the past and is continuing now. The simple past tells us that an action happened at a certain time in the past, and is not continuing anymore. It doesn't tell us anything about when an action happened, so more information needs to be given with this verb form, such as when the action took place. The present perfect tells us that an action started in the past and it is still happening now, or it is something that happens regularly. We may need more information to tell us how long it has been going on. It may also tell us that the time period it started in is still going on. The following example sentences show the different meanings when using the two verb tenses. The sun rose at 6:00 am. (Simple Past: We know that the sun came up at a time in the past and it is not rising now. The sun may or may not be in the sky when this statement is made. The time is important to add.) The sun has risen. (Present perfect: We know that the sun already rose, and it is still in the sky now.) Jackson ate lunch early. (Simple Past: Eating lunch has started and ended in the past. Someone might say this when the time for eating lunch has also ended. Lunch happened early, and it is over now.) Jackson has eaten lunch. (Present Perfect: Jackson started and finished eating lunch in the past, but lunch time is still going on. Someone might say this when others are preparing to eat lunch, and they want to know whether Jackson will join them.) Jeff was friends with Kelly when he was a kid. (Simple Past: This tells us that Jeff is not friends with Kelly anymore, and the additional information tells us when he was friends with her in the past.) Jeff has been friends with Kelly since he was a kid. (Present perfect: This tells us that Jeff was friends with Kelly before now and is still friends with her now. The friendship is continue

"please explain TO me ...." (this is a common error for many students)

Past Simple - the action started and completed in the past ( 5 minutes ago, yesterday, last week, last year , e.t.c) I watched Harry Potter yesterday. It’s fantastic. ( Past Simple, you highlight that you watched this film in the past , YESTERDAY”) Present Perfect - shows the result or the experience that you have now in your life. I have watched Harry Potter! it’s fantastic. ( Here you just want to tell, that now you have an experience of watching Harry Potter, you don’t want to tell when exactly you did it, just tell about the fact, the result l was in Spain last week ( You show that it was exactly “last week”) I have been to Spain ( Your result in General) I have been to Spain but I wasn’t in Spain last week ( At this moment of your life you have the experience of being in Spain, but you didn’t visit it last week)