You're very close. Duration is the span between the start and finish dates of the task. The duration is always based upon the working calendar - so a 10 day duration task may span longer than 10 calendar days - assuming the project calendar has Saturday and Sunday as non-working days.

Work is the amount of effort expended by resources over the duration. It may be more than duration or less. For example: a one day duration task may have 24 hours of work if there are 3 resources assigned, each at 100%. Conversely, a week duration task may only have 10 hours of work if the resource is assigned at 25%.

One way of working with a scenario like yours is to enter the duration and set the task as Fixed Duration (Task Information - Advanced tab). Then assign the resource(s) and enter their work. I'd use the Task Form (split from a Gantt chart view) to be able to enter work for each resource you add.

To echo Guloluseus, if you allow a much longer duration, your resources will delay until the end of the duration. Better to set tighter durations and then use deadlines to monitor progress.