Answer: God’s decrees are the wise, free, and holy acts of the counsel of his will₁, whereby, from all eternity, he has, for his own glory, unchangeably foreordained; whatsoever comes to pass in time₂, especially concerning angels and men.

1. Ephesians 1:11; Romans 11:33; Romans 9:14-15
2. Ephesians 1:4,11; Romans 9:22-23; Psalm 33:11

For further study see:

1. Elder Gregory Moeck of First Orthodox Presbyterian, San Francisco explains WLC 12 (part 2)
   
2. Dr. R.C. Sproul teaches on the subject of God’s Sovereignty: