The document discusses the neurobiology of motivation. It explains that motivation is generated in the brain through the neurotransmitters dopamine, adrenaline, and serotonin. When a person exercises at home, their brain detects a possible reward through dopamine release. This creates an expectation of reward and fuels the sensation of motivation. As the person achieves their goal, such as feeling stronger, they experience a pleasant relaxation sensation from serotonin release, completing the motivational process.