In general, the more complex the plan and the longer its duration, the more opportunity there is for variance to appear.
Variance is the difference between what you intended to happen (as recorded in the plan’s baseline) and what actually happened (as recorded by your tracking efforts).
In Chapter 8, “Track progress: Basic techniques,” you learned how to save a baseline for a plan.
Recall that a baseline is a collection of important values in a plan, such as the planned start dates, finish dates, and costs of tasks, resources, and assignments.
Keep in mind that the purpose of the baseline is to record what you expected the plan to look like at one point in time.
Because it only specifies dates, it is simple, clear and easy information.You can use this flexibility when − You will see Baseline Gantt bars displayed together with the current Gantt bars.As time and work progresses on a project, you might need to change the baseline as well.After the planning is completed, the implementation of the project starts—-carrying out the plan that was previously developed.Ideally, projects are implemented exactly as planned, but this is seldom the case.Resistance to formal tracking of project management data is normal.