Critical path

The critical path of a network is the shortest completion time possible for a job if all tasks are to be completed.

If either of the six day paths is chosen, there is a one day float The float is the time difference between the earliest and latest times an event may start.. This works as an additional day which could be used to start another task a day earlier. This is what is referred to as the float in a job.

Notice how the critical path is now highlighted in red. This is the way to show the minimum time necessary to complete the job.

This is a chart displaying a critical path.
This is the same chart as displayed in 'Start dates'. However, the critical path arrows are shown in red and run from node 1 to node 2 then to node 5.