These are for properties that have septic tanks (Fossa Septica) and contain micro-organisms that help 'balance' your tank.There is a product you can buy from Mercadonna and also Supersol I think called Fossa Septica (or something like that) which looks like tea bags (so I suggest you don't confuse them with real tea bags). You simply throw a couple of these down a loo and flush. We lived in a property that regulalry had foul smelling drains and they did the trick. They cost around €6 or €7.
They will do nothing (except damage your bank balance) if you are on mains sewerage!