Osteoporosis is a bone disease characterized by weakened bones that can break easily from minor injuries, with increased bone loss typically starting in the mid-30s, accelerating in women after menopause. Symptoms may include fractures from minor falls and height loss due to vertebral fractures, which can cause postural changes affecting daily activities and breathing. Preventive measures include adequate calcium and vitamin D intake, weight-bearing exercises, and careful use of corticosteroids.