Farro is the Italian name for a nutty grain of emmer wheat that has its origins in ancient Roman times. It's a whole grain and a healthy complex carbohydrate and when cooked, it's tender and starchy in the way that barley is, meaning it has a soft surface while each grain remains chewy.
Farro is extremely similar to spelt, a more commonly found wheat grain, and in most recipes, farro and spelt can be used interchangably. Some food writers say that farro must be soaked before using, but I've never found that was the case. Instead, when simmered in a generous amount of salted water, farro cooks to chewy tenderness in about 20 minutes, making it a practical weekday dinner ingredient, compared to barley which can take an hour to become tender. If you have trouble finding farro and want to substitute spelt (which can be easier to find since it's sold at health food stores whereas farro is more commonly found at Italian and other specialty markets), be attentive when cooking it because spelt grains can sometimes quickly go from chewy to mushy.
Like barley, bulgur, rice and couscous, farro can be used in a variety of ways. It can be partially cooked and then finished in a pilaf or risotto (Italians call this farrotto). A classic Tuscan recipe is to add farro to a winter bean soup. It's also popular as the main ingredient for salads in which the grain is first cooked, then brought to room temperature, and finally combined with ingredients like diced fresh pepper or tomatoes, onions or scallions, parsley, bits of salty cheese like feta or ricotta salata, and oil and vinegar.
Finally, farro has a nutty flavor, but it's not so forward that it doesn't combine well with other ingredients. That's what makes it perfect for soups and salads.
Until recently, farro was the kind of flavor you might only experience on a vacation to Italy (that's how I first had it, in a salad served at a restaurant in Arezzo, a charming Umbrian city famed for its Piero della Francesca frescoes). But since New York demands global food sources, it's no longer difficult to find here. Look in the same grocery area where rice, bulgar and other whole grains are sold.