Well, these commands are the same as the set ones, but, if not overrunned by the corresponding set command, you may have a camera executing at the same time set and prepare commands, for example, you may be using set to set the target of a camera and, at the same time, prepare to set its position and zoom level. All that in a tight loop.
So, to keep the camera moving with the vehicle you need to set camera position every 0.01 secs with immediate commits, but you want the camera changing targets smoothly, so the immediate commits are not an option. To accomplish that, you move the camera with camPreparePos and camCommitPrepared 0, but you set camera targets with camSetTarget and, for example, camCommit 1. And these commands may be inside a continuous loop with a 0.01 delay.