OREO® chocolate sandwich cookies, manufactured by Nabisco (a division of Kraft Foods), are made up of two oppositely-facing chocolate cookies 1.75 inches wide with 90 notches on the circumference, with your generic Creme FillingTM in the middle. They currently come in original, reduced fat, Mini OREO (bite-size), Double Stuf (twice as much creme filling), and Chocolate Creme (self-explanatory).
One theory about how OREO gots its easily pronounceable name comes from the fact that the cREam is sandwiched between O-shaped cookies:
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cREam
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More fun facts are available at the official OREO site: http://www.nabiscoworld.com/Oreo/