Can someone explain?

[Origomar]

Can someone explain to me what the planes of existance are, i tried reading it and i think i understand it but im not exactly sure. Also what does planetouched mean?

What im not sure of is if there are specific planes or the planes are just a general term for another dimension that has specific qualities. or what planetouched is.

[Altima]

Planetouched means you have been 'touched' by the planes. This can mean you were born on, say, a level of the Abyss, which means you go from being a normal human child to a tiefling, or one of your parents was planetouched or an outsider, such as a djinn breeding with a human to create a fire genasi.

The planes are, well, complicated. Most D&D adventures take place on the Prime Material Plane--the 'real' world, as it were. Every normal world is a prime material plane. In theory, you could hop from Krynn to Oerth to Toril, if you wanted.

Then there are the elemental planes--fire, water, earth, air--as well as the sub-elemental planes, like steam and magma. There's the positive energy plane (positive energy are effects) and the negative energy plane (source of undead). Let it be known that the positive energy plane WILL kill you as well.

Then there are other planes that encompass not elements but alignment. The Nine Hells and the Abyss are the planes of Lawful Evil and of Chaotic Evil, respectively. Each alignment has its own plane, and on these planes are where most deities have their own realms.

Each non-Prime plane also have layers. These are, for all intents and purposes, extra worlds within the layer. The Nine Hells has nine levels. The Abyss has at least six hundred sixty six...explored.

And all these planes are arranged in a neat little wheel with Sigil in the middle.

[Shhalahr Windrider]

The Planes are basically just alternate dimensions. The planes that exist vary from campaign to campaign, but there is a standard D&D cosmology that can be used. I'm not familiar with the setup in fourth edition, so if you are using that system, I can't help you much. They supposedly made some big changes there.

The plane that most campaigns take place on is generally referred to as the Prime Material plane. This is the plane where things tend to be most "normal" and there are few special conditions outside of the standard game rules. Beyond that, there are usually elemental (or "Inner") and Outer planes. It is these planes where Elementals, Outsiders, and even the gods themselves usually make there homes. Most planes outside of the Prime Material tend to have a number of strange conditions that reflect the nature of the plane.

As for planetouched, that is a category of creature that refers to a humanoid with one or more distant anscestors of the Outsider or Elemental type. The extra-planar blood is diluted enough that they don't take on the traits of a half-celestial/fiend/elemental, but strong enough to manifest unique abilities that reflect the nature of the planetouched creature's heritage. Tieflings and Aasimars (http://www.systemreferencedocuments.org/resources/systems/pennpaper/dnd35/soveliorsage/monstersOtoR.html#planetouched) are planetouched that correspond with fiendish and celestial heritage respectively. Elemental planetouched are generally referred to as Genasi (http://en.wikipedia.org/wiki/Genasi).