What is the function of the control rods in the entire fission reactor proccess?

Fuel rods provide fissionable elements such as uranium - 235 , The uranium abosrbs a neutron at thermal speeds (  energy transefered to the moderator) from previous reactions. This then enables the Uranium to go through a fission reaction. The reaction splits the uranium into smaller elements with a higher binding energy per neucleon, neutrons and energy. The neutrons expelled from this reaction create a exponetial increase in the rate or on going reactions. The control rods reduce the reaction rate the further they are lowered into the chamber. The control rods absorb the neutrons to modulate this ratebof reaction.