This tense expresses a period of time or duration that an action has been taking place.It is commonly used to show an action which started in the past and has continued up to the present moment.
The continuous perfect tenses are made up of three parts; The first part can change depending if the tense is present, past or future but the other two (been + present participle) stay the same.
(present) has/have + been + present participle.
(past) had + been + present participle.
(future) will have + been + present participle.
Present perfect continuous: I have been running since early morning on the beach
Past perfect continuous: I had been running for two hours before I stopped for a rest.
Future perfect continuous: I will have been running for fifteen minutes by the time I arrive.