\inside and \outside

According to the ABB "RAPID Instructions, Functions and Data types" manual:

and: 

In other words: WZBoxDef defines a 3-dimensional zone in the shape of a box (WZCylDef defines a cylinder, etc.). Whether you will be monitoring the inside of the box or the outside is defined by the \inside and \outside switch.

If you would define a box somewhere in the space around your robot using the \inside switch and use for instance WZLimSup to limit the zone in which your TCP is allowed to be in, the robot would only be allowed to move inside the box. When the TCP reaches the limits of the box, the movement is stopped as the area outside the box is off limits to the TCP. 

Using the \outside switch, this behavior is the other way around: the robot can move around freely, but its TCP is not allowed to enter the defined box.

If you have a (virtual) system available for testing, you could try defining a world zone, add world zone limit supervision (using WZLimSup) and jog the robot to see which areas you're allowed to enter. Have a look at the WZLimSup examples in the manual to see how that's done.