Enlightenment is education or awareness that brings change, such as your enlightenment about nutrition that leads you to throw out every last bit of your family's junk food.
In Hinduism and Buddhism, enlightenment is also sometimes called "awakening" — after all, the name "Buddha" means "the awakened one." Not all enlightenments are spiritual: your enlightenment about environmental issues, for example, can awaken you to new ways of conserving resources like water and electricity. The Enlightenment started in the 1700’s, a historical era defined by a focus on reason and science.