Glycolysis is a type of anaerobic (does not directly require oxygen) cellular respiration that breaks glucose down into two ATP molecules and pyruvic acid (also called pyruvate) and releases electrons. Glycolysis happens in the cytoplasm of the cell. The electrons that are released in the process are picked up by NAD+ molecules and carried to another part of the cell for another reaction called the electron transport system. Glycolysis is the first step of a series of steps that produces ATP for cellular energy. The pyruvic acid produced by glycolysis is then transferred into another process called the krebs cycle where even more ATP is made.
Source: concepts in biology 12th edition. McGraw-Hill copywright 2007.