Likely the most important feature of Microsoft Project is the calculation of critical path, or Critical Path Method.
Critical Path
The longest path or sequence of project activities that control the earliest a project is expected to finish.
Traditionally, an activity on the critical path has no float or slack, meaning that if the activity is delayed it will delay the finish of the project.
Suppose, for example, that three people are each traveling different routes from point A to point B and would like to know the earliest they can meet together at point B. The person taking the longest path (on the critical path or the longest route) to point B determines the earliest possible time the three can meet together. If that same person takes one hour longer to get to point B than planned, the earliest meeting time is delayed by one hour.
Critical Path Method (CPM)
A simple mathematical method used to determine the duration of the project by calculating the possible paths of activities in a project schedule and identifying the longest path (critical path) in the schedule, or the earliest the project can be expected to finish given everything that must be accomplished.
The Critical Path Method also calculates the amount of float or slack for each activity and sequence or path; identifying how much an activity or sequence of activities can be delayed before delaying the finish of the project.
The Critical Path Method uses a forward pass and backward pass calculation to determine project duration and activity float or slack.
