Classical Antiquity (or Ancient Greece and Rome) is a period of about 900 years, when ancient Greece and then ancient Rome (first as a Republic and then as an Empire) dominated the Mediterranean area, from about 500 B.C.E. - 400 C.E. We tend to group ancient Greece and Rome together because the Romans adopted many aspects of Greek culture when they conquered the areas of Europe under Greek control (circa 145 - 30 B.C.E.)
Gods and Goddesses
For example, the Romans adopted the Greek pantheon of Gods and Godesses but changed their names—the Greek god of war was Ares, whereas the Roman god of war was Mars. The ancient Romans also copied ancient Greek art. However, the Romans often used marble to create copies of sculptures that the Greeks had originally made in bronze.
A rational approach
The ancient Greeks were the first Western culture that believed in finding rational answers to the great questions of earthly life. They assumed that there were consistent laws which governed the universe—how the stars move; the materials that compose the universe; mathematical laws that govern harmony and beauty, geometry and physics.
Both the Ancient Greeks and the Ancient Romans had enormous respect for human beings, and what they could accomplish with their minds and bodies. They were Humanists (a frame of mind re-born in the Renaissance). This was very different from the period following Classical Antiquity—the Middle Ages, when Christianity (with its sense of the body as sinful) came to dominate Western Europe.
When you imagine Ancient Greek or Roman sculpture, you might think of a figure that is nude, athletic, young, idealized, and with perfect proportions—and this would be true of Ancient Greek art of the Classical period (5th century B.C.E.) as well as much of Ancient Roman art.