The concept of lead and lag time is very important when it comes to scheduling the project management diagram. It is crucial for project managers to know about this concept so that they can plan their project as well as execute them within the given time frame.
Lead and lag time is difficult to understand for someone who is not involved in project management. To simplify this, it is important to understand that when one is working on a particular project, it usually involves different incremental phases. Thus, when one activity or phase is completed, only then can the second activity commence.
When the first activity is still active and the second activity is being commenced, this is called lead which is basically the overlap between the two activities. Lag time, on the other hand, is when there is a delay period that occurs before starting the second activity (provided that the first activity is already completed).
Adjusting leads and lags is a technique that is used in project management to bring the activities that are behind (lag) into alignment so that the execution of the project runs smoothly.
This term is defined in the 5th edition of the PMBOK.