I'm new to D&D and I thought I read about teleporting to different planes. How many planes are there and what are they like?
The number and arrangement of planes varies considerably between different D&D campaign settings, different editions of the game rules, and even individual players' games.
However, the most common cosmology is known as The Great Wheel, and is the default in the current D&D 5th edition (Player's Handbook p.300), in the World of Greyhawk and Planescape campaign settings, and in many previous editions of D&D including 3rd edition and earlier.
I recommend reading D&D 5e's Player's Handbook p.300, Appendix C, The Planes of Existence; Dungeon Master's Guide p.43, Chapter 2, Creating a Multiverse; and Wikipedia's entry on Plane (Dungeons & Dragons), which will give the information you need. However, the overview is as follows:
- The world in which the player characters inhabit is the Material Plane.
- Depending on your worldview, you can travel to alternate parallel material planes, or alternate worlds within the same material plane, by various magical means. You can canonically travel between the worlds of different campaign settings, or even to our Earth.
- There are also the Feywild, an alternate Material realm where faeries live, and the Shadowfell, a dark and twisted version of our world.
- There are the Inner Planes, which are made of pure energy:
- The four Elemental planes of Fire, Air, Earth and Water
- The Positive and Negative energy planes are counted Inner Planes, and comprise the source of all life energy as well as the anti-life energy which animates undead
- The Outer Planes, the realms where the gods reside:
- There are sixteen major Outer Planes, including the infinitely-layered Abyss where demons live, the 9-layered Nine Hells, and the realms where the good deities live
- There are potentially other, less well known Outer Planes.
- The Transitive Planes, which allow you to travel between planes:
- The Astral Plane, allowing travel between the planes, traditionally including the travel of souls from the Material Plane to the Outer Planes where their gods reside
- The Ethereal Plane, a foggy realm traditionally allowing travel between the Material and Elemental Planes
- Other planes, including:
- Demiplanes, small planes pocket which can be created by powerful wizards
- The Far Realm, a truly alien landscape beyond the edge of time and space
One generally travels between planes using portals or plane-shifting magic.
However, there are potentially unlimited numbers of planes other than this, and even explaining the existing planes in detail would require multiple entire books. In practice, the exact detail of the planes is up to the individual DM and based on their interpretation of the lore available to them.