Auto bottom up 
The bottom-up approach to planning goes from the specifics to general or, in other words, starts with the most detailed level.
Tasks will behave according to the following rules:
- Parent in "auto bottom-up" adjusts automatically based on its children i.e.:
a. start date of the parent = minimum of children's start dates
b. end date of the parent = maximum children's end dates - If the parent in "auto bottom-up" wants to adjust dates of its children but superior element in WBS does not allow it, then the children may not be allowed to change start or end date.
To learn about other task modes go to the Task modes page.