Nearly every CMYK and RGB color space is defined by a physical thing in real life (IRL). Adobe RGB encompasses what we deem acceptable maximum color gamut for printers. SWOPv2 is a defined space for certain off-set press machines, etc.
Then comes the L*a*b* color space . . . .
I call this color space an organic color space. It’s not defined by a machine but by human perception, thought, and biology. It’s the color-space that every other color must travel through before it can convert to some other space. If you have an image in Adobe RGB and it converts to SWOPv2 CMYK for printing, all those colors must be described in Lab first. In the end, every color we perceive and describe must be communicated through human perception. If we were all deer (capable of seeing UV light) we would have an entirely different L*a*b* color space (it might even be something like L*a*b*uv*). Lab is the universal language dictionary of color.