A mixture of betel leaves and god knows what else - the most pungent thing I've ever tasted and not at all what I was expecting. I managed 2 bites but...not my cup of tea. Often also has tobacco in it and you'll see rickshaw drivers chewing on it for hours and spitting out the red goo that accumulates. Or you can just swallow a bite like I did and avoid a permanent red stain on your teeth.