A single-ply roof is a light-weight thermoplastic membrane, usually white, that can be installed over an existing roof. Sections are fused together with a process called hot-air welding, which creates a watertight seal. The white roof reflects light, rather than absorbing it, which pays off in lower energy costs to power the building’s HVAC system. Single-ply roofs are used in many LEED-certified green buildings

A traditional built-up roof is usually black, constructed in layers with hot asphalt to make it watertight.

The term “green roof” usually refers to a garden roof, which is a building roof that is partially or completely covered with plants that are set in a special growth medium (lighter than regular soil) on top of drainage material, protective layers, waterproof membrane, and insulation.

Check this out for garden roof FAQs:  http://www.carlisleroofgardens.com/Faq.aspx

“Daylighting” refers to the use of a special type of skylight to light building interiors with direct, diffused or reflected sunlight.  Daylighting improves indoor light quality with natural sunlight, thereby improving the health and productivity of the occupants, while reducing energy costs—a daylighting system can pay for itself in as little as two to three years.

Anyone can call himself a roofer simply by picking up supplies and throwing them into a truck. Roofing is not a regulated trade like plumbing and electric.  You should look for an established firm with a demonstrated track record and local references where you can go and see the workmanship.