Present Perfect Simple is formed by combining has/have with a past participle.
|Verb||Present Perfect Simple|
|go||has gone; have gone|
|study||has studied; have studied|
|buy||has bought; have bought|
The Present Perfect always describes a connection between a past action and the present time, but there are three different types of this past-present connection.
1. An action that started in the past and which has continued until now.
I've lived here for four years.
This means I started to live here four years ago, I continued to live here after that, and I live here now.
2. An action which is recent (it happened a short time ago), but which is important news now.
Have you heard the news? Sheila's had her baby! It's a boy!
This means that Sheila gave birth to the child a short time ago, and it's important news now (we have a new baby in the world).
3. An action which happened in the past, but it's inside a timeframe which is past until now.
I've been to Korea, but I've never been to China.
This means that I was in Korea in the past, but I'm looking at my whole life, past until now, and my time in Korea is INSIDE that timeframe. By contrast, I have never been to China inside that same timeframe.