Didymus the Blind (AD 313–398) wrote: “For things of the same substance—ὁμοούσια—have the same activities, and things of a different substance—ἑτεροούσια—have discordant and distinct activities.”
This is a key basis for the doctrine of the Trinity.
Gregory of Nyssa refines the concept here by arguing that through Power, the Father’s activity produces works. Through the Son who is the Power of God, then, the Father and Son share the same activity and so works. See Contra Eunomium 3.4 or Michel Barnes.
So far, all of this sounds like chaotic gibberish! Yes, I know. It is not, however, anything less than a description of the Bible.
So in simpler terms:
God does god-stuff like creating. Humans do human-stuff like being created. Since God has the Power to create and since humans do not, when the Father and Son create, they share something proper to God: the ability to create.
So their activity to create and the work of creation show that they are the one God that the Bible proclaims. John 1:1–3 makes this case. Scripture calls the Son the Power of God (1 Cor 1:24). God creates through Power, the Son.
That is what the Bible said.
So why do Didymus and Gregory sound weird? Because they use Greek Bible words and we are used to English Bible words.
And because they are trying to explain rationally why the Son is truly divine against those who use Scripture improperly to demote the Son to something less than the Power of God.