The objects, not the activity. Also known as anode balls. I gather they are used somehow in electroplating baths to supply the plating metal, but how? And why balls? Seems like the worst way to supply metal, hardly the best.
Balls are used because they provide the best surface area and remain that way generally, throughout their life. If you filled a 2"x 6"x 40" basket with 1" copper balls you would have a much greater surface area than you would if you used a 2x6x40" solid copper bar. When plating, your plating metal (anode) surface area must adhere to specific minimum limits or ratios which depend on the surface area of the substrate (cathode) being plated in order to have proper plating. The positive current supplied to the anode +, knocks off metal ions from the anode and the negative current supplied to the cathode plates it onto the substrate.