A golden age is a time in a specific culture when cultural advancements are at their highest point. For example, many refer to the Golden Age of Classical Greece as a time in the 5th century BCE when literature, drama, philosophy, art and politics were most inspired. These ages are often followed by a decline, where new cultural products are derivative and less inspired and where politics begin to veer off from their initial course. If such ages could be graphed, they would be the high point, the top of the bell on a bell curve, or the apex of a society.
Many people all use this term to refer to a time when a specific thing seems to reach a high point. For example, many look at the 1940s as the golden age of American cinema. Recognizing a high point generally means that something is the best it will ever be, however, and many hesitate to use the term.
In a sense, use of the term is often nostalgic and overly romanticized, particularly in history. For example, not all people who lived in ancient Greece benefited. In particular, slaves and women had few personal or political rights. Generally speaking, however, these time periods are simply a sort of cultural explosion occurs where new developments, and new ideas that benefit society as a whole happen with great rapidity.
Classical Greek literature, for example, is said to have experienced its peak with the dramatists like Aeschylus, Euripides, Sophocles, and the comic playwright Aristophanes. Modern people still read and study their work and find it relevant not only to its own time, but also to the present day. Similar claims can be made about theater in the Elizabethan period, which during which time Shakespeare, Ben Jonson, and Christopher Marlowe all lived and worked.
Golden ages are typically periods of time where one can observe a definite low point prior to and after the age. It is frequently premature to call a new event a golden age, therefore, since without being able to foretell the future, it's impossible to view its decline. The term generally relates to things past and should not be applied to present events or cultural developments.