As with many early ages, the Iron Age was named after the material that their modern tools were made of. Thus in the Iron Age the peoples used iron, as opposed to the Stone Age and Bronze Age. The Iron Age was the last of these three ages as iron is the most advanced tool-making material. The first was the Stone Age and second was the Bronze Age. One cannot put an exact time on when these ages began and ended, because many peoples in the world were secluded and therefore developed these technologies at different times. In the developed world, the iron age began between the 1199 - 700 B.C beginning in places like India, China, the Middle-East, Greece and Central Europe.
This was not to say that there were no iron objects in the Bronze Age, because iron was used, just not commonly. Smelting iron was a very expensive process until the iron age, but it was known to some. At the time, iron was more expensive than gold. One advantage that bronze had over iron is that it is harder to melt iron and therefore harder to craft it into tools. Bronze melts at a lower temperature. This certainly delayed the onset of iron to many civilizations. Another issue that interrupted the use of bronze was that it became less abundant as time went on due to trade issues.
Many iron age artifacts exist and many are still very impressive. The Iron Age brought forth a lot of progress to the people of the world. Tools were more effective and long-lasting. The Iron Age was an age of development and expansion with trading of ideas as common as the trading of materials.