It states the fact of the action or event without regard to its duration. The Present tense has a generally linear action. The Perfect denotes what has begun in the past and still continues . Thus the present and aorist are the basic tenses of Greek. Active voice is something the subject of the verb is doing .
Passive voice is something that is being done to the subject of the verb.
The infinitive is strictly a verbal noun and not a mood. The Greek dunatoi means strong . By adding an a the word becomes just the opposite, which is adunation meaning weak . All three must be present or it is not Biblical belief. The an negates the meaning of the base word.