Verb tense expresses the time in which an action has taken place. Within most texts, the actions described have precise yet subtle relationships in time to one another. It is important that your text correctly represents these relationships.

Present: actions taking place in the current moment (or a moment constructed as current by the text) ex. runs

Past: actions occurring at a definite time before the current moment ex. ran

Future: actions occurring at some time beyond the current moment ex. will run

Present perfect: actions begun at some time in the past and continuing into the present moment ex. has run

Past perfect: actions continuing in the past up to a fixed moment also in the past ex. had run

Future perfect: actions continuing to a fixed moment in the future ex. will have run