How does fermentation allow the production of atp to continue

Fermentation allows glycolosis to take place.

Glycolysis is a process during which, 2 ATP are used to produce 4 ATP, for a net profit of 2 ATP. When oxygen is not present, fermentation allows Glycolysis to continue by creating 2 ATP which are then used to restart the process of glycolysis. Even though the amount of ATP created is small, the process is still able to continue.