The present perfect is a grammatical combination of the present tense and the perfect aspect, used to express a past event that has present consequences. The term is used particularly in the context of English grammar, where it refers to forms such as "I have eaten" and "Sue has left". These forms are present because they use the present tense of the auxiliary verb have, and perfect because they use that auxiliary in combination with the past participle of the main verb. (Other perfect constructions also exist, such as the past perfect: "I had eaten.")
In modern English, the auxiliary verb for forming the present perfect is always to have. A typical present perfect clause thus consists of the subject, the auxiliary have/has, and the past participle (third form) of the main verb. Examples:
I have eaten some food.
You have gone to school.
He has already arrived in Russia.
The present perfect in English is used chiefly for completed past actions or events, when no particular past time frame is specified or implied for them (it is understood that it is the present result of the events that is significant, rather than their actual occurrence). When a past time frame (a point of time in the past, or period of time which ended in the past) is specified for the event, explicitly or implicitly, the simple past is used rather than the present perfect.
It can also be used for ongoing or habitual situations continuing up to the present time (and not necessarily completed), particularly in describing for how long or since when something has been the case. In this case the present perfect progressive form is often used, if a continuing action is being described.
The word "perfect" in the name comes from a Latin root referring to completion, rather than to perfection in the sense of "having no flaws". Perfect tenses are named thus because they refer to actions that are finished with respect to the present (or some other time under consideration); for example, "I have eaten all the bread" refers to an action which is, as of now, completed. However, as seen above, not all uses of present perfect constructions involve an idea of completion.
Source: Wikipedia.org 13:51, 28 November 2005