All in All

I’ve always found the second of these two verses baffling:

For “God has put all things in subjection under his feet.” But when it says, “all things are put in subjection,” it is plain that he is excepted who put all things in subjection under him. When all things are subjected to him, then the Son himself will also be subjected to him who put all things in subjection under him, that God may be all in all. 1 Corinthians 15:27-28 English Standard Version (ESV)

What does: “then the Son himself w...