Explain what it means when a reaction has a positive ΔG

It's a 5 marks question. I can only think of this much. It's obviously not enough.
"ΔG represents the change in free energy (the energy that is available to do work) of the system over the course of reaction. A positive ΔG means that the products contain more free energy than the reactants. So the reaction is endergonic and can’t be spontaneous. The reaction needs the input of energy to make it happen. "
what else can i add?
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