Generally, it can be said that the Indicative Mood indicates the reality or certainty of the action of the verb from the perspective of the speaker. But we must be careful not to think of it as a "statement of fact." Take the sentence "Today is Wednesday." The speaker could be mistaken; the speaker could be lying; or the speaker could be accurate and truthful. It matters not to the grammatical status of the verb. It will be indicative.

Even ideas expressing uncertainty can be in the indicative mood (i.e., 'He is uncertain how to use the Greek moods'). The verb 'is' would be in the indicative mood since 'I' (the writer of this sentence) am certain that ''he' (the one spoken about in the sentence) is uncertain.

The indicative is, by far, the most common mood in Greek texts. Optatives were rare even in Classical Greek and have largely disappeared from the koine. Imperatives (giving commands), by their very nature, are unlikely to be the common stuff of narratives. Subjunctives are often used in complex sentences, in which the main clause will have a verb in the indicative. It is, then, the best guess to assume that the verb is in the indicative mood.

Think of indicating devices - thermometers indicate the real temperature and speedometers indicate the real speed. So the indicative mood is used to indicate the situation, whether the device is accurate or inaccurate.