- drawable-small: ignored, hardly anyone uses phones like that
- drawable-normal-mdpi: older phones with about 3 inch screens, 480x320px resolution, e.g. MyTouch
- drawable-normal-hdpi: most phones with 3 to 4.3 inch phones with 480 wide screens: Droids, Nexus, etc.
- drawable-large: 5 and 7 inch tablets: Samsung Galaxy Tab 7
- drawable-xlarge: 8 to 10 inch tablets, eg. Motorola Xoom, Samsung Galaxy 8.9 and 10.1
Corresponding folders are created for layout, e.g. layout-mormal-mdpi and so on.
The distinction between normal-mdpi and normal-hdpi is very important as these phones have totally different sizes.
In the picture below you can see these sizes being tested with the same content.