We all have been there: printing is exhausting. No matter how nice and good your relationship with your printer is, printing is always a process that tends to be more complicated than easy. Materials, color codes and printing types can be messy and confusing. Whenever I deliver a finished project to a client, I include an easy-to-understand guide to colors.
It's pretty popular. As its name says, CYMK colors are achieved by a combination of 4 colors: Cyan, Yellow, Magenta, and Black. This is a four-color process, meaning the final color is sequentially printed with the four colored inks: it's done with printing tiny overlapped dots to create a certain color. Digital printing works fine with CYMK.
Pantone are solid colors. This means that isn't achieved by mixing colors, but with a premixed ink. To be perfectly accurate, you should work with a Pantone Guide for reference, this code number makes it possible to get the same color no matter where you print. Pantone Guides need to be updated since color can fade with time and can be some variations from time to time. Offset printing is perfect for Pantone codes.
This is an onscreen color code, a very poor choice when printing. It's advised to never use this color code to print since it's developed for screens. It's always better to work in CYMK since RGB conversion to CYMK can turn out to be really bad: you're more likely to notice color and brightness shifts when converting from one to another.