The projection is fundamental in a procedural texture, expecially in a wood texture. Proc textures are 3D textures (like HV) and what you see is a slice created by the intersection between your object and the texture itself. Think at the texture like a huge (even if is infinite) cube in wich you put your object. In the following image you see a plane intersecting a simple wood procedural. In the first one the projecton is set to y, in the second to z and the third one is the same as second except that the texture has an offset in the y direction. It should be clear, looking at images, that a wood text is made by concentrc cylinders (assuming that turbulence is 0 and scale is the same in all axis) that expand from the center of the texture (x0 y0 z0) whose axis is parallel to the projection axis choosed. Hope this helps
