From the help file:
The Task Usage view
The Task Usage view displays project tasks with their assigned resources grouped underneath them. You can use the Task Usage view to:
Assign people and other resources to tasks.
Enter and edit task and resource information together, such as work, start and finish dates, cost, work allocation, and work availability.
Distribute task assignments more evenly across resources.
Find out how many hours each resource is scheduled to work on particular tasks.
Vary the amount of work a person spends on a task by setting work contours.
Split a task so that the second portion of it starts at a later date.
To make the Task Usage view fit your needs exactly, you can customize it or create a new, customized version. When you save your project, the customized view is saved with the project file. To customize the Task Usage view, you can:
Display different task information.
Format individual information to call attention to it. For example, you can apply bold formatting to an important task.
Format a category of information to distinguish that type of information from all other information. For example, you can italicize all tasks on the critical path and increase the size of all column titles.
Change the units of time that are displayed to view your project at the level of detail you need.
View usage information for a specific time period.
Change the horizontal and vertical lines, called gridlines, to enhance the readability or clarity of the Task Usage view. For example, you can specify different line patterns and colors for column and row gridlines.
Create a combination view for the Task Usage view to display additional information about the tasks shown in the Task Usage view or about the resources to which those tasks are assigned.