This plug-in exports the selected image into a CMYK (Cyan-Magenta-Yellow-blacK) TIFF file. This 4-color standard is widely used by paper-publishing companies (and notably scientific journal publishers) to prepare final manuscripts for paper printing.
While converting images from RGB to CMYK is usually done by publishers themselves, some of them may still require you to submit the CMYK versions yourself. If so, this plugin comes in handy: select the input image, it's destination on disk and the profile used to convert from RGB to CMYK (there are multiple profiles available, but if you are unsure, stick with the suggested default profile).
An additional option let's you view each created channel of the final CMYK image after conversion, although note that these are *not* usable by any publisher, and certainly not for image analysis. These are just for artistic effects, if you ever wondered what a CMYK image might look like...