The document discusses the present perfect tense in three main points:
1) It explains when to use the present perfect tense, such as for actions that began in the past and continue to the present, actions that occurred during a period not yet finished, or repeated actions at an indefinite time.
2) It discusses the use of time expressions like "since" and "for" with the present perfect to talk about things that began in the past but continue to the present.
3) It describes using the present perfect with words like "already", "yet", and "still" to discuss events that happened or did not happen at an indefinite time in the past, as well as using adverbs like