My close friend's dad runs a small restaurant where he sells shawarma. I go to their restaurant a lot to eat and to hang out with my friend. Once, his father told me how to make shawarma. He is very proud of his shawarma and I think he was bored that day.
He said that the secret of shawarma is great meat. The meat apparently has to have the perfect ratio of lean meat and fat for it to be delicious. If it's too lean, it'll be too dry and if there is too much fat, it will be too oily.
The other reason that it's good is because it cooks very slowly and evenly since it spins around. It's the same idea as rotiserrie chicken. He also said that shawarma is healthy because while it is cooking, the excess fat melts and drips off of the meat.
I probably didn't need to know so much about shawarma but I'm still glad he told me about it. I didn't realize that shawarma is popular in many countries. If I ever meet an Arab, a Turk or Greek, at least I'll have something to talk about.