Elf-made wine is wine that is presumably brewed by house-elves.
Severus Snape ordered his "assistant" Peter Pettigrew to bring a bottle so he (Snape) could serve it to sisters Bellatrix Lestrange and Narcissa Malfoy when they visited his home at Spinner's End in 1996. The bottle had probably been laying about for a while, as it was covered in dust. When poured out, the color is revealed to be blood-red. Later that year, Rubeus Hagrid and Horace Slughorn drank some wine as a way of respecting Aragog's death.