Resolution is the level of detail in an image. Resolution is defined in printing according to the number of dots per inch (dpi). In digital graphics for the web and on computer screens, it’s defined by the number of pixels per inch (ppi).
In printing, 300 dots per inch, with the image at 100%, will always give you a high quality print job. You can print at lower resolutions, but the image quality declines with lower resolutions. Images at lower resolutions become rough, blurry, or jagged.
Graphics that are prepared for the web and screens are often output at low resolutions of 72 dpi. They look fine on screen but will not print well.