The document discusses the present perfect tense in English. It begins by defining the structure of present perfect sentences as subject + have/has + past participle + since/for. It then explains that the present perfect is used to talk about actions that happened at an unspecified time before now. Examples are given to illustrate uses of the present perfect to talk about experiences, changes over time, accomplishments, uncompleted actions, and multiple actions happening at different times in the past leading up to now. Adverbs that can be used with the present perfect are defined.