Camera sensors
A sensor is a photosensitive surface that reacts to light - either chemically, for film cameras, or electronically for digital.
For digital cameras this is millions of pixels where each of them records how much light they were exposed to in a given period. For this we can also say that each sensor has three main qualities: resolution, size, and “quality”.
Resolution
Resolution refers to the number of pixels in the sensor. In general, higher resolutions allow for printing, while a resolution of 5 or 6 mega pixels