The document discusses insomnia, which is a sleep disorder that causes difficulty falling asleep and staying asleep. Insomnia can be caused by stress, lifestyle factors like irregular sleep schedules, and environmental factors like noise. There are three types of insomnia - acute, transient insomnia lasting 1-3 nights; short-term insomnia lasting less than 3 weeks; and chronic insomnia lasting months or years. Insomnia can be treated through psychological and behavioral techniques like relaxation training. Maintaining a regular sleep schedule, eating healthy, avoiding caffeine, exercising, and reducing stress can help prevent insomnia. While insomnia affects people physically and mentally, there are treatment options available to address this sleep disorder.