What is "the kingdom of heaven"?

Yes, that's the question of the day, and one for which I have not been given a complete answer to yet. It is not a place, note that it is not capitalized, and it also seems to encompass many different aspects. Here's what I've come up with from Matthew:

The kingdom of heaven is like…

a king who wanted to settle accounts with his servants. -Matt 18:23

a landowner who went out early in the morning to hire men to work in his vineyard -Matt 20:1

a man who sowed good seed in his field- Matt 13:24

a mustard seed, which a man took and planted in his field- Matt 13:31

yeast that a woman took and mixed into a large amount of flour until it worked all through the dough-Matt 13:33

treasure hidden in a field- Matt 13:44

a merchant looking for fine pearls -Matt 13:45

a net that was let down into the lake and caught all kinds of fish. -Matt 13:47

The kingdom of heaven will be like…

ten virgins who took their lamps and went out to meet the bridegroom. -Matt 25:1

a man going on a journey, who called his servants and entrusted his property to them. -Matt 25:14

The kingdom of heaven

It is near - Matt 3:1

has been forcefully advancing, and forceful men lay hold of it.-Matt 11:12

Knowledge of its secrets is given by Christ-13:11 19:14

Must be like a child to enter-18:3

Hard for a rich man to enter-19:23