Present perfect используется, что бы описать процесс начавшийся в прошлом и длящийся до настоящего момента. Основной вопрос будет: how long – как долго; на протяжении какого времени. Маркерами времени будут служить: since , for.
Рассмотрим пример
Julia is on holiday in Ireland.
She is there now.
Джулия на отдыхе в Ирландии.
Она находится там сейчас.
She arrived in Ireland on Tuesday.
Today is Friday.
Она прибыла в Ирландию во вторник.
Сегодня Пятница.
How long has she be in Ireland?
Как долго она находится в Ирландии?
She has been in Ireland Since Tuesday.
She has been in Ireland for three days.
Она находится в Ирландии со вторника.
Она находится в Ирландии уже три дня.

Отличие is и has been
Если мы говорим о длительности процесса, который начался где-то в прошлом и длится до настоящего времени, мы используем present perfect. Если наc интересует только данный момент, мы будем использовать present continuous.

Сравнение present simple и present perfect
Present simple | Present perfect simple |
Michael and Anna are married. | They have been married for five years. |
Are you married? | How long have you been married? |
Do you know Mary? | How long have you know her? |
I know Mary. | I‘ve known her for a long time. |
Jason lives in New York. | How long has he lived in New York? He has lived there all his life. |
I have a car. | How long have you had a car? I’ve had a car since June. |
Сравнение present continuous и present perfect continuous
Образование Present perfect continuous
Вспомогательный глагол have been + основной глагол V-ing с окончанием.
Present continuous | Present perfect continuous |
I am learning French. | How long have you been learning French? I have been learning French for three years. |
Fred is watching TV. | How long has he been watching TV? He has been watching TV since 4 o’clock. |
It‘s raining. | It has been raining all day. |