Project, by default, sets new tasks to be manually scheduled. So far you’ve worked only with manually scheduled tasks. In Project, you control the scheduling of tasks in two different ways:
– Work with manually scheduled tasks to quickly capture some details but without scheduling the tasks. Think of a manually scheduled task as an initial placeholder you can create at any time without affecting the rest of the plan. You might not initially know more than a task’s name, and that’s OK. As you discover or decide more details about the task, such as when it should occur, you can add those details to the plan.
– Work with automatically scheduled tasks to take full advantage of the powerful scheduling engine in Project.

When you create automatically scheduled tasks, Project assigns a duration and start and finish date values to them. With automatic scheduling, Project updates calculated schedule values such as task durations, start dates, and finish dates automatically in response to changes in a plan. Changes to factors such as task relationships and calendars can also cause Project to recalculate affected tasks.