I'll have more on fiddleheads in a few days, but I'm still trying to recover from a crash and my computer's a little testy. The short answer to "what is a fiddlehead is that it's a fern". I've got some planted in my yard and in the summer they look great. In spring when fiddleheads come out of the ground, prior to growing up to be ferns they're very tasty. Not all plants that go by the name of fiddlehead are edible, northern Maine happens to be lucky enough to have some of the edible kind.