preload means it comes with the necessary program ialready installed and ready to go. its like computers: if you buy a computer with a new hard drive, you wont get an operating system with it, and the computer will be useless, as you will turn it on and then nothing will happen. but if the computer is preloaded with windows vista operating system, for instance, the computer will work as you expect it to. the angle sensor must be preloaded with its "windows vista" for it to work correctly and make everything run normal.