One of the most useful features of a Gantt chart is to create "dependencies" among tasks. For example, let's assume the following
Task 1 Start date = March 1 End date = March 9
Task 2 Start date = March 10 End date = March 19
If Task 2 can start even if Task 1 is not completed, then there is no need to create a dependency between the two tasks.
However, if Task 2 cannot start until Task 1 is completed, then you'll want to create a "dependency" between them. The benefit of this is that if Task 1 starts later than planned, or takes longer to complete than planned, then when you move the Task 1 task bar in the Gantt chart, then all of the tasks that are dependent, or linked to, to Task 1 will be moved automatically.
In the screen shot below dependencies have been created between all of the tasks. If the Contract Signed date is not March 5 and is moved to March 12, then by moving the purple milestone marker to the right, would effectively push all linked tasks to the right increasing their start and end dates by one week.
Create dependencies
Step 1 Hover over the first task
Step 2 When 2 circles appear at the ends of the task: click on the far right circle
Step 3 Hold your mouse button down and drag the orange line to the the second task.
Step 4 When 2 circles appear on the ends of the second task, release your mouse button when it is hovering over the circle on the far left of task 2
Delete dependencies
Step 1 Double click on the orange dependency line you want to delete
Step 2 When the confirmation delete window appears click OK
