The document discusses the present perfect continuous tense and how it is used to talk about the duration of events that started in the past and have continued up until the present. It provides examples of how to form the present perfect continuous tense using auxiliary verbs like "have" and "been" as well as examples of common uses like describing past experiences, changes over time, accomplishments, unfulfilled expectations, and activities with durations involving words like "for" and "since". It also discusses the placement of time adverbs and the uses of "already" and "yet" with the present perfect continuous tense.