What is meant by God is omniscient?

Being omniscient means that God’s knowledge includes all things past, present, and future, immediately, simultaneously, and eternally, whether things actual or possible.

      This attribute is manifested in

1. The material realm. Job 28:24 (esv)—God looks to the ends of the earth and sees everything under the heavens (so also Heb 4:13).
2. The animal realm. Matthew 10:29—God is intimately aware of the death of small birds.
3. The underworld. Job 26:6 (esv)—Sheol is naked before God, and Abaddon has no covering.
4. The thoughts of man. Acts 1:24—Lord, you know everyone’s heart (see also Luke 5:22; 6:8).
5. Minutiae of personal life. Matthew 10:30—He numbers our hairs.
6. All possibilities. Matthew 11:21, 23—God knows what would have happened had Tyre, Sidon, and Sodom had Messianic revelations.

                        Acts 5:18—The Lord knows all things “from of old.”