Define the difference between effort and elapsed time. What is the importance of this difference for project planning purposes?

Effort is the whole volume of work included in a task and is best thought of like how long this would take to accomplish when one person were assigned to this.  Elapsed time, conversely, is how long the task will take through start to finish and it will depend onto the effort included, how many people are allocated to the task and what delays or external dependencies are included. Exacting and creating an interview report may, for illustration, involve half a day’s effort but obtain two weeks’ elapsed time since the interviewee is slow to review the document and send reverse corrections.  While planning, estimates normally (and rightly) focus onto effort but, while transferring the estimates to the schedules that are the dependency network and bar chart, elapsed time also should be seems.  In particular, issues as fixed ‘lead times’ for acquiring equipment have to be taken in account.