I have lived and worked in Greece for a few years, and worked as a butcher in the U.S. for quite some time, so let me shed a bit of light:
Donair (doner or Donar), Gyros, and Schwarma are all pretty much the same thing. The Doner Kebab (probably the closest original ethnic food to the American invention, the Gyro) is originally from Turkey. The gyro is an American invention which is basically a cheap version of a traditional Greek Kebab (the main difference is that the Greek one would use large pieces of boned lamb, pressed together using its own fat as a binder, and marinated, whereas Gyro uses ground meat.) The Schwarma is a version from the Middle East that is much larger, uses a similar meat to the Greek kebab, but less meat and more vegetables in the kebab itself.
A traditional gyro should be made with at least 50% ground lamb, and the rest beef. The best ground to use is one with a high fat content (this is so that during the remixing it binds and keeps it shape well!). The main flavouring ingredients should always be: garlic, onion, marjoram, rosemary, salt and black pepper. Marjoram and Rosemary are similar to oregano and thyme in flavour (respectively), and are common ingredients in Greek cooking. True Greek food rarely uses oregano. The mass-produced Gyros use oregano, not to mention garlic and onion powder, but we used fresh minced garlic and onions. Here is the recipe we used where I used to work (compliments of Feller's Meat in Clearfield, Utah!)
Posted by WingsFan91 at Recipe Goldmine 6/5/01 12:38:45 pm.
P.S. Tzatziki is made with 500 ml. plain natural or Greek yogurt, 1 cucumber which has been peeled and descended and grated and drained of extra liquid, and 2-4 cloves of fresh minced garlic. Mix together, and let sit in fridge until ready to use. This is an extremely traditional, and might be a bit sharp for the average American palate, so you might want to halve the garlic amount.