The difference between spot colors and process colors.
Spot colors such as Pantone (PMS) colors are specially mixed ink colors. Process color is 4-color (CMYK) that uses varying percentages of Cyan, Magenta, Yellow, and (K)black inks to reproduce colors.
Coated or Uncoated is describing the type of paper you are printing on. Glossy paper is coated and Matte or non-glossy paper is uncoated. You use PMS Pantone Matching System when you need precise color matching because what you see on your screen is not what it looks like when you print the design.
With a PMS book, you can see what the color will look like if you print it on coated or uncoated or if it is converted to RGB or Process CMYK. This book is a must have for any good print designer.
If you have never worried about this before then you have just been lucky and had a good pre-press designer. Since printing with PMS colors cost more than process printing, if you did not pay for PMS then your printer’s pre-press designer converted your design to process for you and had a good eye.
In Adobe Photoshop and Illustrator, they give you PMS swatches and you pick coated or uncoated depending on your output. In the past, before digital printing became the norm, you could save money by printing with black and one spot color. This is because the printer would only be printing two colors, making two plates instead of four. But now that digital printing is so low cost, their is not much if any price difference between printing two colors on a press and digital four color process. Depending on quantity, you can still get a price breat by printing on a press. Ask your printer. Your relationship with your printer and the pre-press designers is the most important for producing top quality print design. They can best tell you how to set your design up to save the most money.