Glycolysis is the process in which glucose is broken down to produce energy.
Compared to oxidative phosphorylation which maximizes the energy potential of one glucose molecule, glycolysis is not as efficient a mode of production of energy.
Glycolysis only produces 2 total ATP molecules for every molecule of glucose.
But, in cells that lack mitochondria or/and a sufficient supply of oxygen, glycolysis is the only process through which such cells can generate ATP from glucose.
Furthermore, glycolysis in maximally contracted skeletal muscle is a rapid and comparatively effective mode of fulfilling short-term energy goals.