A timeline is a visual representation of a series of events. Using a timeline helps put together information that may be intangible, such as time passing or the duration of an event, into a form that is more easily grasped.
A historical timeline shows a sequence of historical events in the order in which they happened.
A timeline can be a representation of the events of a person's life.
Tracking a biological sequence using a timeline can be very educational and helpful in visualizing the sequence. For instance, a timeline can map the process of photosynthesis.
Tracking events horizontally from left to right, like reading a book or using a ruler, is the most common type of timeline.
A vertical timeline is useful to track time and amounts, such as a growth chart or a timeline that tracks money raised for a cause. As time goes on, the line goes up by incremental monetary amounts. This upward motion helps visualize a "gain" in the project.