Shades of Green
Explorer
Its based on very commonplace heroic-fantasy assumptions, concepts and stereotypes. This makes the game's premise (as well asmost D&D settings) pretty easy to explain, and makes descriptions easy. Most concepts touched by D&D are easily familiar to most people who are attracted to such a game: if you've read The Hobbit, LoTR, Harry Potter, EarthSea, Wheel of Time, Narnia or any other popular fantasy book (or watched any sword-and-sorcery movie/TV-series such as Hercules/Xena/Conan/LoTR/Narnia) you'll grasp the basic D&D ideas pretty easily.
This also makes describing settings pretty easy: you only have to focus on describing deviations from the norm (e.g. "in my world, Dwarves live on the rocky shores of a frozen land and raid the rest of the world in Drakkars") rather than the basics and norms themselves (e.g. you don't have to say "Dwarves are short, stocky people with beards and axes who are quite gruff and like alot of ale").
This also makes describing settings pretty easy: you only have to focus on describing deviations from the norm (e.g. "in my world, Dwarves live on the rocky shores of a frozen land and raid the rest of the world in Drakkars") rather than the basics and norms themselves (e.g. you don't have to say "Dwarves are short, stocky people with beards and axes who are quite gruff and like alot of ale").