Usually it means acid-free paper/card, and has an expected shelf life of better than 75 years. Obviously this depends on storage conditions. Atmospheric pollution can fade colours even if the print is kept in total darkness. The type of photo paper you can buy easily for inkjet printers has all sorts of chemicals in it to make it whiter. These react with the dyes/pigments from normal inkjet printers making them fade very quickly, maybe less than ten years or quicker.