Gantt charts originated in the 1910s, when Henry Gantt developed the first one to show the schedule for a project. These charts indicate the beginning and ending dates for a project, as well as the terminal and summary elements of that project, which make up the entire work breakdown. More modern Gantt charts also indicate relationships between various activities.
The left side of a Gantt chart shows a listing of the activities involved in a project, and across the top is a timeline going through the entire expected period in which the project takes place. Beneath the timeline is a bar for each activity, situated beneath the weeks or months on the time line in which that activity should take place. The fact that the bars overlap is helpful for project managers to see which elements take place at the same time.
The first Gantt charts were drawn by hand, which became quite laborious. However, modern project management and spreadsheet software makes it easy to create and edit a Gantt chart for each project under one's supervision. It is also possible to add comments and other information when putting the chart in a shared drive or cloud storage, so that others can view and add text as necessary.