to be + have been, has been + Present Participle (ing-form)
 
Употребляется:
1. Для выражения действия, которое началось и протекало до настоящего момента и продолжается в настоящее время (since — с, с тех пор как).

• What have you been doing since you came to Moscow?

2. Для выражения действия, которое продолжается определенный период времени до данного момента и(или) включая его (for — в течение).

• I have been waiting for you for half an hour.
• I have been translating this text since 9 o'clock.
• Who has been translating the text since 9 o'clock?
• Have you been translating the text since 9 o'clock?
• What text have you been translating since 9 o'clock?
  

Обратите внимание: Глаголы, которые не употребляются в Continuous, стоят в Present Perfect.

• I have known him since 1975.
  
• He has known me for two years.
  
• Have you seen the Petrovs since they left for Moscow?