How are fluorescent colors different then regular colors?

GOLDEN Fluorescent Colors are produced from dyes surrounded by a polymer coating. The photo-luminescence of these colors is caused by the absorption of ultraviolet radiation and shorter visible wavelengths which are then emitted as longer wavelengths within the visible spectrum. These emissions appear as intense, brilliant color. (source)

The above website is for paints, but I think we can probably apply the answer to the dye used to color the poster board.