When you work with digital images, you work with pixels. A
pixel (short for picture element) is the smallest unit of space in a digital
photo, a computer screen, or a printed image.
Every image on your computer is made up of a colored grid of pixels.
Your digital camera records pixels, your scanner converts physical images into
pixels, your photo-editing software manipulates pixels, your computer monitor
displays pixels, and your printer paints pixels onto paper.
The key to successfully editing, scanning, and printing images lies in understanding how pixels transform into inches and vice versa. Resolution is the interpreter between the physical world of inches and the digital world of pixels. When you scan an image, the scanner translates inches into pixels using resolution. When you print an image, the printer translates pixels into inches using resolution.
So what exactly is resolution? Unfortunately, the word is used in different ways in different contexts. "Camera resolution" usually means something slightly different from "image resolution", and "printer resolution" is something else yet again.
Resolution allows you to transform pixels into inches and vice versa
Related Topics:
Which Resolution Setting Should I Choose?
Image Resolution PPI and DPI
Resolution When Creating a New Image
Image Resolution and Print Dimensions
Calculating the Best Resolution for Printing
Why does my image look blocky and blurry?
Printing Actual Pixels using Print Resolution