[Twisted Cluster Bean, Stink Bean, Peteh (Indonesia), Petai (Malaysia), Sa-taw / Sator (Thai), Nejire-fusamame (Japan), Yongchaak, Parkia speciosa]
These beans, about the size and shape of large almonds, grow on large Southeast Asian trees in clusters of long twisted flat pods - about 16 beans per pod. Their taste is often described as "medicinal", but actually it's more like rubber cement - particularly the rubber cement we used to patch inner tubes with back when tires had tubes. They are quite popular in Southern Thailand, Burma, Malaysia and Indonesia where the taste for them has been acquired.
Very young pods are eaten as a vegetable in areas where the trees grow. In northeastern India mature beans are dried for later use and will then be black in color.
More on Beans, Peas and Lentils
Cooking: For curries and the like, I usually put the beans in so they'll cook for 1/2 hour or so which will temper the flavor of the beans and lightly flavor the curry. They soften a bit but remain intact.
Subst: The only reasonable substitute is Mexican Guajes or Huajes, which have a similar taste, but are much smaller and a bit milder. Beyond this there are only "place holders", large fresh fava or lima beans - not at all the same flavor, but at least they're large green beans, and may actually be more acceptable to the uninitiated.