Since no-one has given a decent answer I will (although as RobK said, you probably could have looked in the help file)...
SYNC updates the screen. Basically all the drawing operations are executed at once when you use sync. But first you have to set manual syncing on using SYNC ON (once at the top of your code). You can then set the sync/frame rate using SYNC RATE. If you don't use SYNC ON then DBPro will refresh the screen whenever it thinks it should. It's always best to use manual syncing when dealing with 3D graphics. Eg.
sync on
sync rate 60
make object cube 1,10
do
turn object right 1,0.5
sync
loop
Athelon XP 1600+/Radeon 9600 Pro/256 RAM
