Definition: DPI stands for dots per inch. DPI is a measurement of printer resolution that defines how many dots of ink are placed on the page when the image is printed. DPI does not correspond directly with PPI because a printer may put down several dots to reproduce one pixel. This is because printers use a limited number of colored inks to reproduce an image consisting of millions of colors. The higher a printer's DPI, the smoother your printed image will appear, provided you have a suitable amount of image resolution (ppi).
Today's photo-quality ink jet printers have DPI resolution in the thousands (1200 to 4800 dpi). They will give you acceptable quality photo prints of images with 140-200 ppi resolution, and high quality prints of images with 200-300 ppi resolution.
The term DPI is often used interchangably with PPI, causing a lot of confusion, however, DPI refers to the resolution of the printing device, where PPI refers to the resolution of the image itself.
