Explanation of the Terms Copper, Bronze, and Iron Ages (Source: Wikipedia)

Copper Age

The Chalcolithic (Greek khalkos + lithos 'copper stone') period, also known as the Eneolithic (Aeneolithic) or Copper Age period, is a phase in the development of human culture in which the use of early metal tools appeared alongside the use of stone tools.
Archaeologists generally avoid the use of 'chalcolithic'. They prefer the term 'copper age'[citation needed].
The period is a transitional one outside of the traditional three-age system, and occurs between the neolithic and bronze age. It appears that copper was not widely exploited at first and that efforts in alloying it with tin and other metals began quite soon, making distinguishing distinct Chalcolithic cultures and periods difficult.

Bronze Age

The Bronze Age is a period in a civilization's development when the most advanced metalworking has developed the techniques of smelting copper from natural outcroppings and alloys it to cast bronze.
The Bronze Age first began with Sumer in what is now Iraq, in 3500 BC.

Iron Age

The Iron Age is the stage in the development of any people where the use of iron implements as tools and weapons is prominent. The adoption of this new material coincided with other changes in past societies often including differing agricultural practices, religious beliefs and artistic styles.

Although Iron was used in ceremonial and very limited circumstances much earlier in Mesopotamia, the earliest systematic production and use of iron implements appears from the 14th century BC in the Hittite Empire though recent excavations in Middle Ganga Valley in India done by archaelogist Rakesh Tewari show Iron working in India since 1800 BC. By 1200 BC, iron was widely used in the Middle East but did not supplant the dominant use of bronze for some time.