Original: Homolactic fermentation is the production of lactic acid from pyruvate; alcoholic fermentation is the conversion of pyruvate into ethanol and carbon dioxide; and heterolactic fermentation is the production of lactic acid as well as other acids and alcohols.
Simplified: When yeast ferments, it breaks down the glucose (C6H12O6) into ethanol (CH3CH2OH) and carbon dioxide (CO2).