Activities on the critical path are activities that need to be prioritized in your project schedule. Critical can be different overtime during the project period.
It is essential to know the critical path every time your project schedule is updated, including when updating the actual project schedule.
In Microsoft Project critical path is usually marked with Total Slack (Total Float) zero or marked with the longest path starting from the initial activity of the project to the last activity on the project.
To see the critical path in the schedule that you have created, do the following:
Critical Path on Gantt Chart
Go to the Format tab -> click the Critical Tasks column. On the bar chart, the critical path will be marked with a different color (red).
Also, read about scheduling tutorials using Microsoft Project.
Critical Path on Gantt Table
In the Gantt Table, you can display the Critical and Total Slack columns to view critical activities.
In the Critical column, activities on the critical path will be marked with Yes.
In the Total Slack column, critical activities are marked with the smallest Total Slack or zero.