This is a pretty big question. Consider all the work that first needs to be completed BEFORE a schedule can be constructed.

• What you are going to do needs to be defined.
• Each of the activities needs to be identified.
• Each of the activities needs an estimate of how long it will take.
• All of the activities then need to be put in relation to each other (i.e., what comes first, then what happens after that, and so on)

All this work is done and a schedule can be derived. Why do we do this and how can it help us with our project?