Crashing is a techniques used by project managers to assign more resources/employees in order to complete a task/job faster hoping that the increase in cost will help in offsetting the time needed to complete the task/job. Fast Tracking on the other had is project's managers technique to assign more than one task/job to be done at the same time instead of working on them one after another. This is a technique known to increase the risk as something might go wrong leading to the extension the project time line