Image resolution
From The Glossary of Digital Photography
The total number of pixels in an image, expressed as pixels per linear distance, such as pixels per inch or pixels per millimeter. The image resolution is a measure of the amount of detail available in an image. In lens measurement charts, the resolution is expressed as line pairs per millimeter where the measurement describes the smallest amount of separation between two lines that can be resolved or seen through a particular camera-lens combination. Image resolution is also sometimes expressed as the total number of pixels in the horizontal direction by the total number of pixels in the vertical direction. A sample would be 3040 x 2016, which means 3040 pixels in the horizontal direction by 2016 pixels in the vertical direction.
