They are about the size of peanut shells (groundnuts) and are actually a small tuber. They are fibrous and can be peeled, but it's not necessary. They are used to make Tiger "milk" and a drink that is popular in Spain where they are also grown.
I like them. They remind me of the Chinese chestnut trees that my grandparents had at their place. You know, the chestnuts that people use to roast or put in their Thanksgiving stuffing? Like those. Street vendors sell them to motorists in very slow traffic.
The ones we get here are fresh and raw. Inside their creamy color just adds to the chestnut similarity. More juicy than a chestnut and sweeter, they are great for snacking on. Kind of reminds me of eating carrots in texture, but more like celery without the strings - but sweeter. Getting your fiber with these little gems will not be a problem.
If you ever get a chance to try some, I recommend it - fresh and raw are best, of course. But for those of you who don't have access to them, you'll just have to imagine it.
Links to click on for more information...A very good overview and descriptive article:
Tiger Nuts (article in encyclopedia format)
by Dianne Mason
A company that sells them commercially from Spain, with good information throughout their site: