Please see this screenshot from Acrobat DC, and explain as if I were 15 years old.
When you convert colors, you use some algorithm to change one color to other. I.e. You can change from one colour space to other.
When you map colors, what you do is specify target color and then specify destination color without any algorithm behind. You can map green spot to yellow or vice versa, but it is very unlikely that you will find color spaces where in first color would be green but in second - yellow.
As the use of the words "powerful" and "flexible" may well imply, this option is "complicated" and is mostly aimed at the more professional end of the print production spectrum. Here are some examples of how you might use it:
- A designer supplied you a PDF that was RGB. In order to print it, you need to convert it to CMYK. A print profile defines how the conversion of each colour is performed, giving different CMYK breakdowns for the same RGB colour, depending on the profile. This could be done with an industry standard profile such as FOGRA39 or with a bespoke profile that is specific to your machinery, company, site, etc
- You have a PDF that has been created using a standard profile (such as FOGRA39), but you want to apply a bespoke profile for accurate proofing and printing.
- You want to apply specific changes to the way a PDF is colour separated. For instance to change the maximum ink coverage (when CMYK colours print on top of each other) or reduce the overall amount of ink to compensate for dot gain (darkening of print on press).
Note: while these tasks can be done in Acrobat, and often are as part of a PDF workflow, they are commonly handled by more professional (and eye-wateringly expensive) pre-press software.
This allows you replace specific process colours with other process colours. For instance:
- In flexographic printing, there is thing called 'minimum stable dot' which means tints below a certain percentage cannot be printed well / at all. You could use this function to hunt the document for all tints below (say) 5% and boost them to 5% so that they print or remove them (make them 0%) so that you get a clean edge.
- If a separated colour is printing 'dirty' because it contains a small amount of a certain colour. i.e. 100% yellow + 20% magenta + 5% cyan, but you want a clean, warm yellow then you can eradicate the cyan from the elements using this colour to clean up the result.
- If you are trying to match a spot colour out of process and you have a better (because you know it's a closer match on you printer) CMYK split than the one used in the document, you can swap one CMYK split for the other.
Map spot and process colors
This one is handy for swapping or combining spot colours. For instance:
- Your document has more than one named black colour. i.e. 'black', 'Pantone Black' and 'Text Black'. If you need them all to print on one plate, then you can map them all to process black, for instance.
- You have one or more corporate document that use Pantone 295 blue for all the text, diagrams etc, but the company style guide changes to demand Reflex Blue be used in all cases instead. You can update all the elements that use this new corporate colour using map colours.
There are myriad other uses for these functions, or combinations of these functions, especially when they used as part of an automated workflow. For most designers, all of these functions fall into the "almost never need them, but once in a blue moon they might just save the day" category.
Hope my answer helps, and thanks for teaching me something in return: ELI5. Never heard that before, had to search for the meaning.