Thanks #Bilal . You gave the examples which are present perfect continuous, like-I have been watching movie for 30 minutes.But i was talking about present perfect tense.

Thanks # wendy Now since i know that its not only my confusion, so i wouldn't stress on myself which to select out of two.

Hey Sodium, there are different times when you'd use either one of the tenses, but to keep things simple, usually you'll use the simple past when you want to talk about something you did in the past that has been completed in the past. It's not happening anymore. For example: 1. I drank a cup of coffee last night. (You drank the cup of coffee last night and you finished doing that act last night. It's not happening anymore.) 2. I watched a movie this morning. 3. I went outside to buy a newspaper. All three of these sentences are talking about something(s) that happened in the past and these things are no longer happening. For the present perfect, we're talking about something that started in the past, but continues into now. 1. I have been drinking this coffee for an hour. (In this sentence, the person started drinking coffee an hour in the past and he/she is still drinking the coffee now). 2. I have been watching the movie for 30 minutes. (They started 30 minutes ago and they're still watching the movie). 3. I have gone outside to buy a newspaper. (The person went outside at some time in the past to buy a newspaper and they're still outside now). So to sum up. Simple past= started and finished in the past. Present perfect= began in the past, but continues into the present. As I said, there are other ways to use the tenses (specifically the present perfect), but these are the basics. Hopefully that helps.

This is even difficult for native English speakers. Many speakers will use simple past tense, even when it would be proper to use present perfect. It may not be proper, yet we understand each other. So, do not worry if you do not always use perfect grammar in English. It is a very difficult language to perfect, even for native speakers. I do not know a single native speaker who always uses correct tense.