A timeline is a representation of events listed in chronological order, or the order that they happened in time. There are many different timelines used, but one of the more common representations involves a line or bar with the chosen time scale written along the line (or as part of it), with some visual or text description of the event that occurred at that time. Below is one of the most basic examples of a timeline:

The events, as well as the time scale, can be just about anything, such as the years that key points in the history occured, the schedule of speakers at a conference, weekly fitness goal progress, or key events in the life of a person.

Often, the time scale is linear, as in the example above (1 year intervals) but it does not have to be; in some cases logarithmic scales are used. Generally though, the width of the intervals on a timeline indicate the passage of time with relation to each other. In the above example, all of the intervals are the same width because each interval represents 1 year.

Timelines can also be vertical, not just horizontal. Below is an example of a vertical timeline where some of the events occur at varying intervals of time:

In the above example, the timeline shows some of the events that occur from the time John wakes up to the time he gets home from school. Although not all of the events occur at equal time intervals, the length of the intervals in the timeline are proportional to the passage of time. In other words, the length of the interval between 7:00 AM and 8:00 AM is the same of that between 9:00 AM and 10:00 AM; a 30 minute interval is half the length of a 60 minute interval, and so on.

Even with these two basic examples, you can see that there is a lot of flexibility in how to construct a timeline, so it is possible to be creative with color, images, and more when presenting information in a timeline.