Binky is a white horse owned by Death, being a living breathing creature. Death chose him because the other horses that he tried, including the traditional skeletal horse and a fiery horse both iihyg4g5g7h7h6v5gyvyvyd impractical, as the skeletal horse kept falling apart and had to be held together by wire and the fiery horse kept setting his bedding on fire.
Presumably Binky will one day also die. However, because he spends much of his time in Death's Domain where time does not exist, his death is unlikely to occur for a very long time.
Binky is also extremely fast, being able to travel from the disc to space in moments, and was able to travel millions of miles without stopping (Although time did not exist in that place).