Definition of DPI, pixel and PPI

Dots per Inch (DPI) is a measure of printing resolution, in particular the number of individual dots of ink a printer or toner can produce within a linear one-inch space.

A pixel (abbreviation for "picture element") is one of the many tiny dots that make up the representation of a picture in a computer's memory or on a television screen. Therefore, PPI (Pixels per Inch) is the number of pixels that make up a linear one-inch space in the memory of a computer or on a television screen.