Sensors can detect smallest changes in the quantity they are measuring, and this tells us the resolution of a sensor. Usually, resolution of sensor output is equivalent to image resolution and screen resolution output. Accuracy of a sensor can be much worse than its resolution. Characteristics of a sensor have big influence on resolution of a unit.
Mainly in digital imaging any resolutions (sensor, image, screen) are measured in pixel count or number of total pixels. For example, when you see in the specification resolution 800 x 600, this means 800 pixels in width and 600 pixels in height. Another measurement you get when you calculate pixels in width and pixels in height – 800 x 600 = 480,000 pixels or 0.48 megapixels.
Pixels size and amount of pixel defines displays resolution. The size of 1 pixel in the display is described by pixels per inch (PPI). The smaller the size of pixels and larger the number of pixels the higher the resolution. The higher resolution, the better the quality of image.
Source: Pulsar (CMOS sensor)