In Maya, UV texture coordinates (UVs) can be created for polygon surface meshes using the following UV mapping techniques:
Each UV mapping technique produces UV texture coordinates for the surface mesh by projecting them onto the surface mesh based on its inherent projection method. As a result, the UV texture coordinates have an initial 2D spatial correlation to the vertex information in the 3D world space coordinate system. It is this correlation between the texture map and the surface mesh via the UVs that positions the texture on the surface.
The initial mapping produced via the above UV mapping techniques does not usually produce the final UV arrangement that is required for a texture. As a result, you will often need to perform further editing operations on the UVs using the UV Texture Editor.
The polygon and subdivision surface primitive types in Maya have default UV texture coordinates that can be used for texture mapping. However, if you modify the default primitives in any way (that is, scale, extrude faces, insert or delete edges) you will need to map a new set of UV texture coordinates onto the modified object to suit your texture mapping requirements.
The best workflow is to map UVs onto a model only when the it is complete.