THE KINGDOM OF GOD
Jesus came into Galilee Proclaiming the gospel Of God and saying, " the time is fulfilled and the Kingdom Of God is at hand; REPENT and believe in the gospel. When asked to define His Kingdom, Jesus explained it this way: The Kingdom Of God is not coming in ways that can be observed. The Kingdom Of God is in the midst of you." (Luke 17:20-21). Romans 14:17 says that the Kingdom Of God is a matter of Righteousness, peace, and joy in the Holy Spirit.
THE KINGDOM OF HEAVEN
The Kingdom Of Heaven is within us: Jesus spoke His Word, "The Kingdom Of God is in the midst of you refers to His being the King and that He was in their midst advancing His Kingdom through His teaching, including the Sermon on the Mount, and the signs and wonders that are also illustrated what His Kingdom would be like. So, Jesus was teaching the Pharisees and others that the Kingdom was available to them, within their reach if only they became His disciples. It's an implicit reference to their made in the image and likeness of God ( Gen 1 26-27) and thereby had the God-given ability to cooperate with God's grace to make the Kingdom Of God a reality.
THE KINGDOM OF GOD WITHIN
"Whosoever shall confess that Jesus is the Son Of God, God dwelleth in him and He in God."
1 John 4:15