The character I am talking about is a bird.
It wanders because I want a behaviour where a bird can move around in space that must look natural. So I can't just make it move at a certain direction. It needs to turn sometimes (sometimes turn more etc) by a random angle.
That is the bird I talked about.
Now, in 2.5D, to implement that Wander behaviour I could create a circle that the bird is at its center.
Then, an imaginary target would be moving around the circle, each frame moved by a small angle (random).
Then that target is used as the target of a Seek behaviour to make the character (the bird) move toward it.
In the image above that blue dot represents the imaginary target that rotates around the player. The blue arrows show the direction at which it can move. But that is in 2.5D.
The above behaviour makes the bird able to rotate around the Y axis only. I want it to be able to rotate around the X axis (that would make it move up/down as well as left/right).
So I used a sphere to do this, but I want to be able to set the pace at which the imaginary target rotates around, so that I can make the bird move "more" left/right than up/down. Because a point on a sphere is defined by two angles in polar coordinates, I tried to make one of them smaller that the other. But because x and y of the coordinate depend on both angles, changing one affects the rotation of the target in the other "direction". I hope it is clear now