What does ΔG° refer to exactly?

[![enter image description here](https://i.stack.imgur.com/bQsgt.png)](https://i.stack.imgur.com/bQsgt.png)


My interpretation of this image is that $\Delta G^\circ$ is equal to the difference between $G^\circ$ of the products and $G^\circ$ of the reactants.


But, I've also read $\Delta G^\circ$ as being given for calculating the difference in free energy between a point when $Q=1$ and the equilibrium position. That is, $\Delta G^\circ=-RT\ln(K)$. 


Which one of these is the accurate interpretation? 


