Demand is the hours the roles require, whether or not someone has been booked. Confirmed bookings show supplied commitments. The difference exposes work that remains unfilled. Don't substitute booked hours for demand: an empty schedule can still contain a large client requirement.
A pipeline forecast can show full demand or multiply role hours by the probability of the work proceeding. Both views are useful when their assumptions are labeled. Weighted demand is an expected planning measure, not permission to staff only a fraction of a won engagement. Compare the forecast with qualified capacity for the same weeks. Quarter totals can hide a short peak shortage, so inspect the weekly view before deciding how many people to hire. A provisional reservation shows a possible named resource but doesn't remove unfilled confirmed demand until the commitment becomes confirmed.