The Age of Enlightenment refers to the 18th century in European philosophy, and is often thought of as part of a larger period which includes the Age of Reason.

The term also more specifically refers to a historical intellectual movement, "The Enlightenment." This movement advocated rationality as a means to establish an authoritative system of ethics, aesthetics, and knowledge. The intellectual leaders of this movement regarded themselves as courageous and elite, and regarded their purpose as leading the world toward progress and out of a long period of doubtful tradition, full of irrationality, superstition, and tyranny (which they believed began during a historical period they called the "Dark Ages"). This movement also provided a framework for the American and French Revolutions, as well as leading to the rise of capitalism and the birth of socialism. It is matched by the high baroque era in music, and the neo-classical period in the arts.

Another important movement in 18th century philosophy, which was closely related to it, was characterized by a focus on belief and piety. Its proponents attempted to use rationalism to demonstrate the existence of a supreme being. In this period, piety and belief were integral parts in the exploration of natural philosophy and ethics in addition to political theories of the age. However, prominent Enlightenment philosophers such as Voltaire and Jean-Jacques Rousseau questioned and attacked the existing institutions of both Church and State.

The 18th century also saw a continued rise of empirical philosophical ideas, and their application to political economy, government and sciences such as physics, chemistry and biology.

According to scholarly opinion, the Age of Reason preceded the Enlightenment (if it is thought of as a short period), and the Renaissance and Reformation preceded it (if it is thought of as a long period). Furthermore, Romanticism followed the Enlightenment.
Taken from Wikipedia