Introduction - If you have any usage issues, please Google them yourself
Quoted on Android dip, dp, px, sp, and other units instructions
Dip: device independent pixels (equipment independent pixels. Different equipment have different display effect, this and equipment hardware, generally we in order to support WVGA, HVGA and recommended the QVGA, do not depend on the pixels.
Px: pixels (pixel). Different equipment to display the same, generally we HVGA represents 320 x480 pixels, the use of more.
Pt: point, is a standard length, the 1 pt = 1/72 ", used for printing, very easy to use
Sp: scaled pixels (enlarge pixels). Mainly used for best for textsize font.