Project management milestones occur when crucial stages are reached, such as the completion of a major report or the delivery of goods to the client. While the project stage's result typically takes much work to make happen, the milestone itself has no effort given it. Rather, a project management milestone is a measuring point in the work process. Often planned in the early stages as check points, milestones don't just mark the time line, or stage, of a project, but also its direction.
For instance, in the examples above of a milestone being a completed report or a client delivery, the project manager may have scheduled a change in direction of what the next step should be based on those results. If the report turned out to be missing something important, a decision as to which employee would be responsible for quickly fixing the error would have to be made. If the client wasn't satisfied with the delivered item, arrangements for a sales representative to discuss and correct the issue would have to be made. Such project management milestones will then cause a change in the direction of the process to accommodate new decisions made to reach necessary objectives.
If a project management milestone is used only as a check point rather than also scheduled as a possible needed change of direction, a small issue along the way could affect the ultimate goal. If only project management milestones are checked, smaller details could go unnoticed at first and make everything appear to still be on time when in reality it wouldn't be. For instance, on a construction project, the point at which materials are delivered could be considered one of the major project management milestones. If it is left at that though, checked off the list without making sure everything is there to complete the construction on time, these details could cause a large problem.
In the original project plan, if this type of milestone also has a check point scheduled, missing problems are much less likely. This makes project management milestones much more crucial that just a measurement, but also a valuable planning tool. Catching problems quickly, then changing direction to deal with them promptly, can keep a project on track without disrupting the entire plan or schedule.