In English, if anything is complicated it is the tenses. I believe, it is that part of the English structure that always leaves us perplexed. Hence, one should understand what tenses are before one could dive into the depth. Whenever we use verbs in a sentence, we use three different time zones. One that is going to happen, the one that is happening, the one that has already happened. In English, these three are termed are Future Tense, Present Tense, and Past tense.