Spelt is a particular type of wheat with characteristic nutritional properties. It is particularly high in protein (generally around 15%) and tends to have lower amounts of gluten than most species of wheat. Spelt wheat was actually farmed for centuries in ancient times and has fallen out of favour recently due to a range of factors, including the fact that more modern wheats have a higher yield. However, some people with wheat allergies find that they can tolerate spelt. This is why this ancient crop, which was unfashionable until recently, has suddenly become a health food.
Spelt has a "heavy" feel to it which some people like, because it is quite a filling wheat. It can be used to make most wheat-based products, particularly pasta and crispbread.