small, normal, large and xlarge are screen SIZE
small: QVGA (320×240)
normal: HVGA (480×320)
large: VGA (640×480)
xlarge: larger than HVGA(720x960)
ldpi, mdpi, hdpi, xhdpi, xxhdpi and xxxhdpi are screen density (number of pixles in inch).
LDPI: Low density, ~120 dots per inch
MDPI: Medium density, ~160 dots per inch
HDPI: High density, ~240 dots per inch
XHDPI: eXtra High density, ~320 dots per inch
XXHDPI: eXtra eXtra High density, ~480 dots per inch
XXXHDPI: eXtra eXtra eXtra High density, ~640 dots per inch
For example, you may have a large
screen with mdpi
resolution.
Handsets are often small or normal 7" and 10" tablets are large.
Read more:
http://en.wikipedia.org/wiki/Pixel_density http://en.wikipedia.org/wiki/Graphics_display_resolution http://en.wikipedia.org/wiki/Display_resolution http://en.wikipedia.org/wiki/List_of_mobile_phones_with_HD_display