Pantone/PMS colors are used for spot color¹. If you're not designing for spot color print reproduction, you wouldn't need this. If you want to translate a specific RGB color to a Pantone color, there are sites like https://www.ginifab.com/feeds/pms/ which can make suggestions.
> Thanks, so this is an extension/generalization of the CMYK colorspace?
As a spot color standard focused on the printed (or otherwise reproduced) result, I think it's most useful to think of PMS as its own thing.
CMYK is the standard 4-color "process" model, in which those four colors are combined to create all colors possible by mixing them. In contrast, Pantone/PMS colors are solid colors and reproduced as such (rather than as combinations of CMYK), and include colors that fall both inside and outside what's possible with CMYK process printing.
For example, Target red is "PANTONE PMS 2035 C" when printing to coated¹ paper. For printed pieces, designers at Target can specify that as a spot color and know that the reproduced result will match this. This same red can be approximated as a halftone of all 4 CMYK colors, but the result won't look as sharp or vibrant.
Professional/industrial printers can have up to 10/12 inks and pigments, plus metallics, and varnishes. you also then have different optical characteristics depending on substrate. It’s so far removed from the cmyk colour space.
¹ https://en.wikipedia.org/wiki/Spot_color