The whole topic of color management can get pretty dry and technical, but stick with it because there’s information here that’s useful and puts lots of other things in context.
This is the system used by computers and other digital devices for defining colours. In photography, the RGB system is almost universal – colours are defined using red, green and blue colour ‘channels’. In printing, it’s CMYK, or cyan, magenta, yellow and black. Some image-editing processes use Lab mode, which consists of a ‘lightness’ channel and two (‘a’, ‘b’) colour channels.