A project isn't done when the work is done — it's done when the longest chain of dependent tasks is done. That chain is the critical path: it sets the finish date, and every task on it has zero slack. Map your tasks and what each one waits on, and this finds the path that's really driving the timeline.
5 of 6 tasks set the finish: Discovery → Design → Backend → Integration → Launch. Slip one and the whole schedule slips. The other 1 task has slack to absorb delay.
Each bar starts as early as its dependencies allow. Coloured bars are on the critical path; a faded tail shows how far a task could slip — its slack — before it would move the finish date.