I just learned the difference between spices and herbs a few weeks ago while preparing to talk about them in a class on Food & Eating in the Roman World. I couldn't believe I had not looked that up before. Also learned that the same plant can provide both spice and herb, like dill, in which we use the leafy parts (herb) and the seeds (spice), and the plant that provides cilantro (herb) also provides coriander (the spice, from the seeds). I can't wait to learn more!