Neurons in worms get activated by light and specific smells, aiding in their navigation using a technique called steering. Evolution utilized smell gradients to enable navigation, where the concentration of molecules is high near food and decreases as one moves away. By applying simple rules of moving forward towards higher smell concentrations and random turning towards lower concentrations, worms can find the source of food. Steering categorizes things into good and bad, helping worms navigate towards food smells and away from predator smells.