There are ways to display, including printers, tablets, smartphones, monitors and many others. They all use some kind of resolution measurement, including pixels per inch (ppi) and dots per inch(dpi), to gauge output density. Dpi is typically used for printed resolution and ppi for image or display resolution.
Laser-class printers produce completely different size and shaped dots than their inkjet counterparts do. The output of a good and appropriately configured laser printer is so clean, in terms of halfones and screen frequency, that theoretically it can be used as camera-ready art or color separations for the purpose of reproduction on a printing press.
Devices that output hard copy, such as printers, plotters, slide recorders and imagesetters, print at different rates of dots per inch. Take laser printers for example. Most laser printers print at rates between 150 and 600 dpi. But some models prints at rates of 1200 dpi and beyond. Imagesetters print at rates from approximately 900 up 3,000 dpi and beyond. High resolutions mean smaller and tighter dots, which ensure more subtleties and detail of halfones screen and photographs.
Bitmap and vector are the only two types of computer graphics. You may be more familiar with bitmap graphics. JPEG and PNG are both bitmap graphics. Bitmaps are device dependent, which means that they maintain the resolution of the device which creates them. Increasing or decreasing a bitmap image’s size will greatly influence the density of the dpi.
Vector graphics are drawn mathematically. Every line, fill and curve are created via thousand or even millions of computer instructions. Increasing or decreasing a bitmap image’s size will not affect the density of your picture because when you reduce and enlarge vector graphics, they will redraw themselves.
Keep in mind it is important to know your phones’ resolution and image type so that when you print them as standalone photographs or put them in your documents you’ll know the way to display them in their best quality. If you inadvertently print 72 dpi photos on a photo printer which has the capability of much higher resolutions, you will get much lower quality documents and images.