Work vs. Duration
An important (and sometimes confusing) concept in assigning tasks is the distinction between the duration of a task vs. the hours of work required to complete the task. DURATION is simply the calendar time (of working days) that is spanned from the start of a task to the completion of a task. If a task starts at the beginning of Monday and ends at the end of Tuesday the same week, its duration is 2 days (or 16 hours in Projects, which schedules based on an 8-hour day).
WORK is the amount of labor that it will take to complete a task during its duration. So, in our above example, if the actual amount of time it will take to complete the task is 8 hours, then the work for the task is 8 hours (or 1 day), while the duration is the 2 days over which the work occurs.
NOTE: If you are unable to view the Work or Duration columns in the main Projects area, an Administrator may need to enable those fields to display.