A lot of times when a project is in its earlier stages (the conceptualization phase), the people that control the money at an organization (the CEO, CFO, CIO, Business Manager, etc.) want the best estimate they can get regarding the time and cost of a software development project. Again this may be very early in the project lifecycle, some time just after someone said, "That sounds like a good idea" and well before the project begins. In short, they want the best "back of the envelope" ("ballpark") cost estimate you can give them.
