It’s a 3rd party freeware ASIO driver. You can download it from the guy who created it directly. It is presumably the most installed ASIO driver of all times. Google ASIO4ALL.
After installing it in Cubase you need to go to menu Studio → Studio Setup → Audio System
Do yourself the favor and read the manual on how to set up your system correctly. It is really worth it, even though it might sound boring.
https://steinberg.help/cubase_elements/v12/en/Cubase_Elements_12_Operation_Manual_en.pdf#_OPENTOPIC_TOC_PROCESSING_d8429e40551
In case the problem is still present after doing the above, please refer to this guide on how to setup Windows correctly (I just assume that you are a PC user):