VISION MODE & SET UP
The P2V comes set in Vision 2 mode. There are two 3 position toggle switches on the transmitter. In this mode only the right hand switch (S1) does anything. Toggling it on-off multiple times puts the Phantom in compass calibration mode which you need to do before your first flight in a given part of the world (aka, the compass dance - involves rotating the Phantom on two different axes). Part of setting up the Phantom requires downloading two apps to a PC (Windows is covered, Apple support seems to be lagging somewhat). One of these apps is used to configure the Phantom, the other to configure the controller. Configuration is where one can switch from Vision 2 mode to NAZA mode.
NAZA MODE - S1 SWITCH
In NAZA mode the right hand switch (S1) allows you to select Vision 2 / GPS mode, Attitude mode, and initiate RTH or select Manual mode, the latter choice being made in configuration. Manual mode is generally reserved for those who have excellent skills or a (Phantom) death wish. Attitude mode essentially disconnects the GPS feature - the craft will roughly hold it's "attitude" based on compass and altimeter sensors, but it will drift with the wind. Initiating RTH means invoking the return home feature without having actually lost the control signal ... basically the pilot is telling the Phantom to fly itself directly home. In manual mode one is essentially flying a quadcopter with the technological assistance of several years ago, i.e., a bit of gyroscopic stabilization, but little else.
NAZA MODE - S2 SWITCH
In NAZA mode the left hand switch (S2) allows the pilot to choose between IOC (Intelligent Orientation Control) off, IOC home lock, and IOC course lock. With IOC off, the craft is directionally operated like any other RC craft, forward is the direction the "nose" is pointed, back is the direction the "tail" is pointed, left is to its left, right is to its right. An issue with traditional RC flight is once the craft gets far enough away (or flys into the sun) its VERY easy to lose track of how it's oriented ... is it facing toward me, or away from me? Once you lose orientation your only recourse is to give a command and see how it reacts - could mean disaster. The other issue with traditional RC flight is reversing your control. When the craft if flying away from you, all's right with the world. If you want to go to your right, you push the stick right ... BUT when the craft is coming toward you and you want to go to your right, you push the stick left because your right is now its left. This can get very confusing and dangerous, especially when you're about to crash, are in personal panic mode, and are trying to recover. Enter home and course lock. In home lock, it doesn't matter which way the craft is oriented (pointing). Back is always back to the home point (where it took off, usually where the pilot is), forward is always away from the home point, right is always 90° to the right of a line from the home point to the craft, and left is always 90° to the left of a line from the home point to the craft. Think of the craft as being on the end of a string which is the radius of a circle - shorten, it comes back; lengthen, it goes away; twirl (left or right), it goes in a circle around the home point. Similarly, in course lock, it doesn't matter which way the craft is oriented (pointing). But now forward is whatever direction the craft was pointed before it took off. It's like flying on an invisible, fixed grid. If it took off with the nose pointing north, forward will always send it north, back will always send it south, left will always send it west, and right will always send it east. Two caveats for home and course lock to work, 1) the pre-flight must've been completed (the Phantom got a home point and direction fix), and 2) the Phantom must be flying at least 10 meters (66 feet) away from the home point. Note - you can change the home point and course lock direction after takeoff while in flight, but that's info for another time (maybe check the IOC topic).
A caution - many who "have been this way before" strongly recommend that you learn to fly well in Vision mode before going to NAZA mode. Two reasons: 1) It is extremely easy to inadvertently hit S1 or S2. If you do this in NAZA mode and don't realize you've done so, the Phantom will not be flying as you expect and panic may ensue ... bad things will then happen. 2) While these aids can be quite useful, they are a function of the complex electronics in the Phantom - if they should fail in some way, you need to have some basic skills to fall back on.
I suspect it's not in the documentation because the Phantom 2 Vision is sold as a "simple to fly" mobile camera and they didn't want to complicate it any further in that regard. Fortunately the electronic brain they used in the P2V was their NAZA-M controller, and they did provide a means to switch to the NAZA mode. I suppose they figured anyone who was capable of using the added features would seek out the required info. Check out the DJI Wiki at
http://wiki.dji.com/en/index.php/Naza-M_Setup_Wizard for more NAZA-M info (all may not apply to the P2V).