A selection of adaptors to convert one type of lamp connector to another - some of which could result in the lamp exploding.
Lamps (or light bulbs) are available with a wide variety of connectors. In most applications is is easier to just buy a lamp with the correct connector on it, but it is sometimes useful to convert one connector to another.
In many cases, this conversion is not a problem. For example a bayonet B22 to an Edison screw E27 - both are of similar physical dimensions and are generally used with the same voltage.
However some of these adaptors enable low voltage (230V) lamps to be connected to extra low voltage (12V) outlets. Doing so is not danngerous, but obviously the lamp will not work, raising the question as to why such an adaptor would even exist.
Far worse are those which are the reverse - connectors typically used for 12 volt lamps being connected to those normally used for 230V mains. Using such a device will inevitably result in the lamp failing instantly, often with explosive results.
These adaptors are apparently made for use with energy saving LED lamps, which replace other types of lamp such as incandescant and fluorescent. Some of these LED efforts do use what would be considered the 'wrong' voltage, so could be safely used with one of these adaptors.
However this is not really an answer, since as with any lamp, it would be far better to manufacture it with the connector appropriate to the voltage required rather than the added expense and complexity of using an adaptor.