UV Project assigns texture UV coordinates to the Source geometry for use in texture and bump mapping. UVs are projected onto the geometry via a transformed projection geometry.
The effect of this operation is best visualized in the UV viewport, or with textures turned on in the 3D viewport. Then you can use the interactive handles to position an incoming texture using this SOP.
UV Project creates the UV texture attribute if it does not already exist. The attribute class (Vertices or Points) is determined by the Group Type. It is recommended that UVs be applied to vertices, since this allows fine control on polygonal geometry and the ability to fix seams at the boundary of a texture.
For closed mesh Bezier & NURBS surfaces, projections with boundaries will result in seams. UV Texture can be used to open these surfaces automatically. Alternatively, convert the surface to polygons using a Convert operation prior to applying UV Project.