When we use it?
To describe an experience.
Ex: Andrew has met the doctor.
Ex: I have never been to your house.
To describe a change over a period of time.
Ex: James has grown since two years ago.
Ex: This hairbresser has become very popular.
To describe accomplishments.
Ex: Man has been to the moon.
Ex: The mobile phone has made it possible to chat online.
A continuing action that started in the past.
Ex: Paul has worked here for 4 years.
Ex: We have been in a relationship for 2 days.
Has (he she it)/have + past participle and regular and irregular verbs