A glossy photo paper is often smooth and has a very highly reflective surface. Lustre paper offers a reflective surface and has texture to it. This paper often shows colors as being more saturated and higher values of contrast, and is appropriate for digital printing.
Glossy photo paper will have a very shiney, very bright, high gloss surface. Lustre surface photo papers will show less gloss, but will not be defined as matte surfaced. Think of the lustre surface as being related to the satin finish often described with painted surfaces.