I saw this ingredient (farro) listed in a recipe that I was interested in making; however, I've never seen nor heard of it before.  Could you explain what it is, please. What can I substitute for Farro? 
Most farro enthusiasts would say that there is NO substitute for farro.  More realistically, you certainly have options.  It would help if you clarified what type of recipe you were interested in making - in the absence of that information, I would suggest you consider barley if you're making a soup and quinoa if you're making a salad.  The cooking times for both of these would differ from the cooking time for farro. 