Hello and welcome! As Larry and Ken noted, they are used for a lot more than just pizza - anytime you want indirect, they are the ticket.
In my other thread from today I used them with beef ribs - you can see them in the first picture. Often I'll just use a piece of foil over the D's to keep drippings from getting on the ceramic (say, if I'm cooking chicken), but today I went overboard with a couple of drip pans. I used these since I knew the ribs would be dropping a lot of fat over a long period of time.
- Mike