[sailingdog]

Corelle, IIRC, was a trademark of the Corning Glass company, and refers to their line of dishes that are made from Corelle, which is basically tempered and laminated glass. From the Corelle website:

About Corelle ProductsMaterials

VitrelleTM glass – the original Corelle material that is known for its strength, durability and versatility.
Vitrelle 1:

Our Vitrelle and Vitrelle2 products are made in a hub lamination process that thermally bonds three layers of glass together. The core glass in the middle and a top and bottom layer of very clear skin or glaze glass. This lamination results in glassware that far exceeds the normal strength of any single glass composition. Simply put, lamination does for glass just what it does for wood. It yields a finished product that is much stronger than the individual components from which it is made. We are so confident in the strength and durability of our dinnerware , we offer a THREE YEAR warranty against breaking and chipping to the Vitrelle glass dinnerware and will replace any item under normal household use that does.

Melamine is a plastic resin. From the Wikipedia entry on it:

Melamine resin or melamine formaldehyde (also shortened to melamine) is a hard, thermosetting plastic material made from melamine and formaldehyde by polymerization. This plastic often is used in kitchen utensils and plates (such as Melmac and is the main constituent of high-pressure laminates, such as Formica and Arborite, and of laminate flooring. Melamine-resin tile wall panels can also be used as whiteboards. Melamine resin often is used to saturate decorative papers that are directly laminated onto particle board; the resulting panel often is called melamine and often is used in ready-to-assemble furniture and inexpensive kitchen cabinets.

Not the same thing at all... one is made of laminated glass, the other is plastic resin.

Melamine resin dishware isn't really all that safe for use in Microwave Ovens... as seen here, here, and here. Corelle, AFAIK, is perfectly safe for use in the microwave oven.