There are basically two methods of scheduling, the Critical Path Method (CPM) and the Program Evaluation and Review Technique (PERT). In a sense, the CPM techniques owe their development to the widely used predecessor, the Gantt Chart. But the Gantt Chart has certain limitations:
The Gantt Chart has limitations in visualising.
It cannot work for projects that include more than 25 activities.
Also, the Gantt Chart provides no direct procedure for determining the Critical Path, which is of great practical value to identify bottlenecks and/or delays.
The Critical Path is defined as the longest series of activities (that can’t be done in parallel) and which therefore governs how early the project can be completed.