Upload & Sell: On
HDR is a method to autoblend different exposures. You can save all the raw files, but the result is only saved as a JPG.
Multi exposure is more like what we used to do with film cameras, it is designed to get different stuff in the same image. You could do an eclipse of the moon sequence for example and get the moon in different locations with everything else stationary.
The method I am describing is probably not an intended use, or at best undocumented. But by averaging several images, it enhances real detail while cancelling out random noise.
The average setting keeps the exposure constant. Other options are additive, bright and dark. Additive would build the exposure. I have not explored the others.