If a task is effort-driven, as resources are added or removed on the assignment, the work remains constant for the task and is redistributed among the resources. For fixed-unit tasks, for example, if more resources are assigned, it may take less time to complete the task. Resource calendars Microsoft Project schedules assigned resources based on working and nonworking times, indicated on their resource calendars. Unlike work resources, assigning material resources to a task does not affect task scheduling. In this case, changing the work of a variable material assignment can change the task duration.
Work is different from task duration.
For example, a resource may require 32 hours of work to complete a task, but the task may be scheduled with a duration of two days. In this case, more than one resource needs to be assigned to this task. Working eight hours a day on the task, two people would complete the task in two days. As soon as you assign a work resource to a task, work is calculated for the assignment. The way work is calculated depends on whether the task is effort-driven.