We’ve already looked at the three main tenses in English: the past, the present, and the future. Or two tenses, if you don’t consider the future a tense. But in addition to tense, there’s another element to referring to time in English, and that’s aspect. There are three different aspects in English, each of which can be combined with a tense (and sometimes another aspect), and they are: simple, continuous, and perfect.
I’ve already covered simple and continuous in writing about tenses, and they’re fairly straightforward (I go, or I’m going), but the perfect aspect is a little trickier. Before getting into the details, have a look at the following pairs of sentences: