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 colors. In photography, the RGB system is almost universal – colors are defined using red, green and blue color ‘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’) color channels.