grammar

Use the Simple Past to express the idea that an action started and finishedat a specific time in the past. Sometimes, the speaker may not actually mentionthe specific time, but they do have one specific time in mind.I saw amovie yesterday.I didn'tsee a play yesterday. Use the Present Perfect to say that an action happened at an unspecifiedtime before now. The exact time is not important.I haveseen that movie twenty times.Ithink I have met him once before. Use the Past Perfect to expresses the idea that something occurred beforeanother action in the past. It can also show that something happened before aspecific time in the past.I had never seen sucha beautiful beach before I went to Thailand.Idid not have any money because I had lost my wallet.

There are lots of grammar reference material available inthe internet, it is better to google for the information you need rather thanto raise question and wait for hours to get the answer, many of the answersgiven in this site are wrong either in concept or in sentence structure or in both. The following is an example extracted from one of theanswers. Do you understand it?“It's commonly used, but of course 'I have noteeth to eat with' will be more political correct for grammar police, lol”

佢地個 tense 唔同
Past tense: they found that
Present perfect tense: they have found that
Past perfect tense: they had found that

唔會就咁p.p.架, 通常以下情況會用p.p.
1. Present perfect tense (現在完成式): has/have + p.p.
2. Past perfect tense (過去完成式): had + p.p.
3. Passive voice (被動式): be + p.p.