The Resource Sheet table presented below Gantt Chart shows a time phased distribution of the work for resources and their assignments.

For each resource and assignment, in the Assigned row, you will see overallocated resources (resources programmed to work on all the assigned tasks more than is possible, according to their calendars and MaxUnits values) marked with the red color and the resources that have overtime work (work scheduled for a resource beyond its regular working hours) marked in yellow. In the same time, the table indicates the assigned task and the time interval where/when the problem occurs.

In the Available row, the working hours of the resources with no assignments are marked in green color.

Depending on the situation, there are a few methods to solve the overallocations (level resources):
1. Remove resources or decrease Units value for some of the resource's assignments until their sum does not exceed the MaxUnits value. If needed, available resources can be added (available hours are shown in green color). To do this in the current view select the appropriate task, open Details window for the lower pane, click Resources tab and make the necessary modifications.

Hint: To keep constant the task work, before any assignment modification select Try to keep the work when changing resources/duration (make task work-driven) checkbox at the bottom of Resources tab. This way, the duration of the task will change automatically to accommodate the work with the assigned resources.

2. Move one or more tasks, if you consider the lack of resources as a constraint. You can also link tasks that require the same resources, although it's not recommended. In both cases a note on the task would be useful to remind you the cause of the action.

3. Increase the MaxUnits value (employ more resources with the same role), if the work has to be done in the scheduled time. In this case, the name of the resource should indicate a role rather than a human resource.

The combination of Gantt Chart and Resource Sheet is also useful to make a fair distribution of the work even though the resources are not overallocated.
Hint: In Details window you can see resource/task details, depending on your currently selected element in the table.