Resolution refers to the number of pixels in an image. Typically, resolution is identified by the width and height of the image as well as the total number of pixels in the image.
Image reference of pixels:
The standard resolution for web images is 72 dpi (dots per inch). However, this resolution is considered very low when it comes to printing. Images/files at this resolution will have a blurry print output.
For printing, the industry standard and recommended resolution for all images and art files is 300 dpi. And 200 dpi is generally considered the minimum standard for high quality photographic reproduction in books and magazines.
(An adorable puppy named Cola from our colleague Ellis. From the comparison image, it's clear that the image quality at 72 dpi is quite blurry)