Dots per Inch (DPI)
Dots per Inch (DPI), a measurement of resolution, refers to the number of dots a printed photo contains per square inch of space. The more dots per inch means that the photo has a higher the DPI and, therefore, has a higher resolution. Photographs with greater resolutions appear more refined, smoother and are generally better quality.
DPI is a term that refers to photo printers, as well as computer monitors and scanners. However, a single printer is not necessarily limited to a specific dots per inch measurement. Many photo printers can be set to different DPI parameters, depending on the quality you want for your finished print.
Pixels per inch (PPI), while related to DPI, refers to the pixels per inch on a computer monitor. When printing a photo, remember that your DPI setting on your printer must be set substantially higher than your PPI setting: while computers can produce multiple colors within a given pixel, your printer can only print a single color within a given dot. Consequently, if you want your picture to print similarly to the manner in which it appears on your monitor, turn up your dots per inch setting on your printer.