Parameters that establish how tasks are leveled around other tasks. Three options are available:
1. ID Only - Priority will be given to tasks with the lowest ID numbers (usually those earliest in the schedule).2. Standard (the default) - Microsoft Project considers slack values (both free and total - a task with more free slack time is delayed first, followed by ones with total slack), dates (later starting tasks will be delayed before earlier-starting ones) and constraints (as they affect the schedule and the critical path). 3. Priority, Standard - Microsoft Project will apply user-defined priorities as the primary factor in deciding which tasks are to be delayed. Tasks with equal priorities will then be delayed according to the 'Standard' parameter above.
SOURCE: microsoft project glossary-projectlearning.net