The document discusses the present perfect continuous tense (also called the present perfect progressive tense). It is used to talk about an action that began in the past and is still ongoing or was ongoing up until the present moment. Some key uses are to talk about actions that have been in progress for a specific period of time, repeated actions that started in the past and continue to the present, and actions that ended just before the present time. The present perfect continuous emphasizes the ongoing nature of the action, while the present perfect simple tense emphasizes the result of the action.