Mark 12:35-37 How is He Both David's Son and David's Lord?

Mark 12:35-37 (NKJV) Jesus: How Can David Call His Descendant Lord? (Matt. 22:41–46; Luke 20:41–44) 35 Then Jesus answered and said, while He taught in the temple, “How is it that the scribes say that the Christ is the Son of David? 36 For David himself said by the Holy Spirit: The LORD said to my Lord, “Sit at My right hand, Till I make Your enemies Your footstool.” ’ 37 Therefore David himself calls Him ‘Lord’; how is He then his Son?” And the common people heard Him gladly.