Amber
1.
Amber is a series of 10 books written by Roger Zelazny in the 1970's. They chart the story of Corwin, one of the Princes of Amber, a magical world which is the only true reality in the universe, all other things, including earth, being merely distorted reflections, or shadows of Amber. In the course of the book Corwin visits various other worlds, including Earth, in all of which he has the powers of a God, including the ability to create and destroy a world.
This series has proved very popular with gamers, and many games show its influence, featuring systems with multiple worlds and super-powerful characters.
2.
Amber is a roleplaying system based on the Amber books. It made itself famous even before its publication by being entirely diceless, and ushered in an era of systems that concentrated more upon the act of role-playing than on systems of rules. It is, in essense, the first storyteller system.
Amber campaigns distinguish themselves by being highly complex and unmanagable, almost always threatening the entire universe with destruction by unimaginably powerful forces.
David Donachie
See Amber as a Genre.
So here goes, the definitive definition of amber, possibly.
Amber is a diceless role-playing game where you take the part of the characters, or their relations or adversaries, in the books by Roger Zelazny. Hmm okay, now I'm a bit stumped, look is like they are gods, sort of, and well its Amber...
My only suggestion is try reading the books.
Matthew Barrowcliffe