The document discusses the difference between using the present perfect and past simple tenses in English. It provides examples of when to use each tense, including talking about experiences without a specific time reference, completed past actions often with time references, unfinished ongoing actions, and recently completed actions in the recent past with adverbs like "just" and "already". It also discusses using the present perfect with words like "for" and "since" to indicate the duration of unfinished ongoing actions.

1. PRESENT PERFECT vs PAST SIMPLE