People are usually torn between the desire to have a flashy label that will unmistakably call out to customers, and some awkward hesitation at having such “screaming” color on their product. Fluorescent labels are certainly the most distinguishable among labels and are usually used for special purposes, for example, labeling objects that need to call out some warning (medical labels, hazard labels).
Fluorescent labels are also known as day-glow or neon labels. More than any other label - glossy, clear or brightly colored - these labels are made to attract attention. However, they should not be used for all purposes. For example, it’s unlikely you will see a wine bottle or a barcode label on some technical object in any of the standard fluorescent color, like pink, orange or green.
Basically, you will use fluorescent labels for any product that should be noticed faster than if labeled with other types of “regular” labels, because they are designed to be conspicuous. Since they are usually made out of paper or flexible vinyl, they are known for being very customizable: you can die cut them into almost any shape you desire.