A kingdom is a place or government where a king rules and reigns over his people. In Scripture, the kingdom is the government or universal dominion of God. (1 Chronicles 29:10-12 , Psalm 145). At this present time, the kingdom of God is within His people Luke 17:20-21 and not like the kingdoms of this world John 18:36. God rules and reigns through his Son Jesus Christ himself (John 18:37 , 1Timothy 6:13-16 , Revelation 19:11-16, John 12:12-15 , Luke 23:2-3 , Luke 1:31-33)
Just as the people of an earthly kingdom should submit to the will and law of their king. Even more so should we submit to the will and law of our King. In fact we cannot be a part of his kingdom unless we submit to His will Matthew 7:21.