What does 2 Samuel 7:18-29 mean?

Then King David went in and sat before the LORD and said, “Who am I, O Lord GOD, and what is my house, that you have brought me thus far? And yet this was a small thing in your eyes, O Lord GOD. You have spoken also of your servant’s house for a great while to come, and this is instruction for mankind, O Lord GOD! And what more can David say to you? For you know your servant, O Lord GOD! Because of your promise, and according to your own heart, you have brought about all this greatness, to make your servant know it. Therefore you are great, O Lord GOD. For there is none like you, and there is no God besides you, according to all that we have heard with our ears. And who is like your people Israel, the one nation on earth whom God went to redeem to be his people, making himself a name and doing for them great and awesome things by driving out before your people, whom you redeemed for yourself from Egypt, a nation and its gods? And you established for yourself your people Israel to be your people forever. And you, O LORD, became their God. And now, O LORD God, confirm forever the word that you have spoken concerning your servant and concerning his house, and do as you have spoken. And your name will be magnified forever, saying, ‘The LORD of hosts is God over Israel,’ and the house of your servant David will be established before you. For you, O LORD of hosts, the God of Israel, have made this revelation to your servant, saying, ‘I will build you a house.’ Therefore your servant has found courage to pray this prayer to you. And now, O Lord GOD, you are God, and your words are true, and you have promised this good thing to your servant. Now therefore may it please you to bless the house of your servant, so that it may continue forever before you. For you, O Lord GOD, have spoken, and with your blessing shall the house of your servant be blessed forever.”

English Standard Version (ESV)