In Project management, What are leads and lags used for?

The terms leads and lags are used to identify and control the timing of various activities within the project. It is important to accurately document leads and lags.

Lead Time: Let's assume a project has two pieces that need to be completed at the same time. Work package A will take4 weeks to complete, but work package B only takes one week. B would show in the project plan as a finish to start (FS) with a one week lead.  This means the B work package component should start one week before A is scheduled to be completed.

Lag Time : Lag time can best be described as a planned or forced delay.  A great example of this is a construction project that involves pouring concrete. The project plan must include a lag time of2 days for the concrete to dry before the next phase can begin.

Lead and lags are used for activities , tasks ,objectives,  goal , Strategy and plans especially in timing and time plans