Summary of the Koiné aspect

The two major aspects of NT Greek are the present and the aorist. The present reflects an internal viewpoint concerning the occurrence which focuses on its development or progress and sees the occurrence in regard to the details of its make-up, without beginning or rend in view, while the aorist present an external view of the occurrence in summary, from beginning to end, without regard for its internal make-up. The perfect, on the other hand, is a complex verbal category which, in one point of its basic meaning, shares the aspectual sense of the aorist. It combines three elements in its invariant meaning: the Aktionsart-feature of stative situation, the tense-feature of anteriority, and the aspect of summary viewpoint concerning the occurrence.—Verbal Aspect in New Testament Greek, page 420 (emphasis original)