The simple answer to the question, what IS gravity? may be answered with words like the Higgs Boson particle. Don't be fooled. That's circumstantial evidence. The Higgs Boson particle is the mode of action of gravity, not its cause.
What is Gravity?
Deducing Gravity
Gravity is fundamental to the working out of God's plan for creation. So how on Earth did we manage to deduce that gravity was created on the second day? There are three parts to this logic:
October 24th
On the first day God said "let there be light," in a body of water called "the deep," which was formless. On the ISS, in free fall in the gravitational field of Earth, water forms a sphere so the first day was Zero-G.
Propitiation
Propitiation is the price paid for our redemption. This was Jesus himself. He lived a sinless life and his sacrifice was sufficient to pay for the sins of the whole world.