That's for the Apple 30-pin to 8-pin Lightning adapter (model MD823ZM/A), which allows you to connect older devices with the 30-pin dock connector to newer devices with the Lightning connector. Here's what it looks like:
This adapter is particularly useful if you have an older iPhone, iPad, or iPod that you want to charge or sync with a newer Mac, iPad, or iPhone. For instance, it's compatible with:
However, it's not compatible with newer devices that use the Lightning connector only, such as:
If you're looking for an adapter for one of those devices, you'll need a different model.
I hope this helps! Let me know if you have any other questions.