This 12 W transformer belongs to the cabinet lighting collection and ensures that lamps which cannot be connected directly to 230V mains still operate easily. Its output is 12V (the voltage the cabinet lighting spotlights run on), and the plug on the input side connects directly to the wall socket. It is part of a plug and play system, together with the spotlights from the collection.
Take care to ensure that the total connected wattage does not exceed the transformer's maximum capacity.