The term “kingdom of heaven” or “kingdom of God” meant different things to different people in New Testament times. What it meant to Jesus appears to me to be different from what it meant to the early church, the Gospel writers, and even the Twelve.
On the one hand, I will set forth below what it meant to everyone but Jesus. On the other hand, if the reader is content to accept what I just said without proof, the reader may be happiest to skip the rest of this chapter, and the next, and instead go straight to “Jesus’ words about ‘the Kingdom‘”. Some of this stuff gets really technical.