Energy comes in many forms - heat, light, chemical, electrical, mechanical, nuclear, etc.
When we calculate free energies under these conditions, we use the superscript o . Energy from oxidation reactions is stored as lipid and carbohydrate and reclaimed when we oxidize these metabolites. We call the oxidation of metabolites catabolism and the reactions are catabolic. Catabolic processes are exergonic - they occur spontaneously. When we synthesize metabolites, the reactions are generally reductions and the process is called anabolism and the reactions are anabolic.