The English tense-aspect system has two morphologically distinct tenses; present and past. The word tense refers to the time period in which the verb of a sentence places an action. For the grammatical tense, there are subcategories called aspects. Aspect refers to the duration of an event within a particular tense. In other words, the aspects: Simple, progressive, perfect, and perfect progressive.
No marker of a future tense exists on the verb in English; the futurity of an event may be expressed through the use of the auxiliary verbs "will" and "shall", by a present form plus an adverb, as in "tomorrow we go to New York City", or by some other means. Past is distinguished from present–future, in contrast, with internal modifications of the verb. These two tenses may be modified further for progressive aspect (also called continuous aspect), for the perfect, or for both. These two aspectual forms are also referred to as BE +ING and HAVE +EN, respectively, which avoids what may be unfamiliar terminology.
(While many elementary discussions of English grammar classify the present perfect as a past tense, it relates the action to the present time. One cannot say of someone now deceased that he "has eaten" or "has been eating". The present auxiliary implies that he is in some way present (alive), even if the action denoted is completed (perfect) or partially completed (progressive perfect).)