Visualise Tex Coords
Visualise normal and visualise tex coords are shaders which give an RGB representation of the 3D vector (the surface normal or the texture coordinates). The R value of the colour is the X component, G is Y, and B is Z. Surface normal values which range from -1 to +1 are remapped into the visible range 0 to 1.
UV coordinates from imported geometry usually only occupy X and Y, therefore blue is usually 0. They usually range from 0 to 1. But if applied to terrain or other procedural object, tex coords are XYZ. There is a repeat option for the texture coordinates because they are not limited to just the 0 to 1 range on procedural objects; this option causes the values to repeat within the 0-1 range.
A vector is a set of three scalars, normally representing X, Y and Z coordinates. It also commonly represents rotation, where the values are pitch, heading and bank.