In simple words, PPI (pixels per inch) is the means of measuring resolution where the created image has an artificial source of light (TV’s, phone displays, projectors, etc) DPI (dots per inch) is the means of measuring resolution on printed paper or other media. Displays work with RGB color model, printed media works with CMYk color model. CIElab color model is used as a reference point for translation between one and the other...like when you see something on a monitor, hit print and hope to get the same result on paper and what you’ve seen on the monitor. Resolution (PPi, DPi) is the density of the pixels used in a system. Pixels are the smallest element of a display system or a print system, pixels vary greatly between systems and technologies. The seizures get worse and worse once you get deeper into these things as imaging is a complex subject.