A Gantt chart (sometimes called a bar chart )is a simple chart which links activities to be performed with the timing of those activities.It is a key element in project management.
Why use it? To help plan the use of resources over time.
When used? In planning projects and in getting people to think about the implications in terms of resources of their proposals.
How used? The figure below shows what a bar chart looks like for a simple project. The descriptions on the left hand side are of the individual activities and the lines (bars) indicate both the duration and the timing of activities on a calendar basis.