Gantt charts show the start and finish dates of the elements of a project. Gantt charts show dependency between activities. It means that some activities can begin only after other activities are finished. If activities are independent, they can go on at the same time (though the converse is not necessarily true). Gantt charts can be used to show current schedule status using percent-complete shadings and a vertical "TODAY" line as shown here.
They are now a common charting technique, but Gantt charts were thought revolutionary when first introduced. The charts are also used in information technology to represent data that has been collected.