The present perfect continuous tense is used to describe actions that started in the past and are still continuing in the present or have recently stopped, with a focus on the duration or continuity of the action.

Structure
The structure of the present perfect continuous tense is:

Subject + has/have + been + verb(-ing)

- "Has" is used with singular subjects (he, she, it).
- "Have" is used with plural subjects (I, you, we, they).

Usage of present perfect continuous tense - 
1. To show an action that started in the past and is still continuing in the present
   - Example: They have been studying for hours.
     - (This indicates they started studying some time ago and are still studying now.)

2. To emphasize the duration of an action
   - Example: I have been working here for five years.
     - (This emphasizes the period of time the action has been happening.)

3. To describe recent actions with visible results or effects
   - Example: She has been painting, so the room smells of paint.
     - (This implies that painting was done recently, and its effects are still present.)

 Examples of present perfect continuous tense
- We have been waiting for the bus for twenty minutes.
- He has been reading that book all afternoon.
- They have been playing soccer since this morning.
- I have been feeling tired lately.

 Time Expressions Often Used
Common time expressions with the present perfect continuous tense include:
- for + a period of time: for two hours, for a long time
- since + a specific starting point: since morning, since 2015
- lately or recently: recently, lately

 Key Points
- Emphasizes the duration or continuity of an action that began in the past and is still ongoing or has just ended.
- Requires has/have been followed by a verb in the -ing form (present participle).

The present perfect continuous tense is particularly useful when you want to focus on how long an action has been happening, especially if the action still affects the present.