A timeline is one way of showing a chronology (putting time in order). It can cover a short period of time or hundreds of years.
A detailed Timeline showing the Norman and Plantagenet Monarchs and some of the main events of their reigns.
Timelines are useful in History because they give us an overview of a period of time and can help us to see how events are related. For example, using the timeline above, we can see that the Battle of Agincourt in 1415 was part of the Hundred Years War between France and England.