Baseline Overview :
Once you build the complete project plan with all your estimations, now you are ready to execute the project. During your projectís execution phase, resources are working on your project and they will perform their assignments as per your estimations.
Are you sure that they are working as per your estimations? Is your projectís tasks are getting complete as per your initial planning? Is your project current cost is within thresholds of your budget what you planned at the beginning of the project? Is your project is on schedule or behind schedule?
To answer all these questions, it is necessary to compare your current projectís status with originally planned. It means, prior to execution of the project, you have to make your all initial estimations as check point to compare with future progress of the project.
Baseline is the snapshot of the schedule that can be used as reference point against which you may compare actual progress. It means, your original plan will be treated as baseline.