The major planes are ordered by negative to positive energy: The Abyss, Earth, Water, Shadow, The Material Plane, Feywild, Air, Fire, Elysium.
Traveling between the inner planes (Shadow, Feywild, Material) is easier than traveling to the elemental (Fire, Water, Air, Earth) or outer planes (Elysium, Abyss). The Shadow and Feywild being very close to the material means it is not uncommon to see parts of the material plane mirrored into them.
There is additionally the ethereal plane, astral plane, and the veil, which are special and adjacent to all other planes. The astral is often used as a conduit between other planes, and the veil and ethereal are both home to spirits and souls.
Travel is easier between the inner planes (Shadow, Etherael, Material, Astral, Feywild). To the outer planes, it is considerably easier to open portals from the inner to outer, rather than the other way around. While the feywild and shadow planes are seperate planes from the material, it is not uncommon to see parts of the material plane mirrored onto them. The shadow plane is inhabited by dangerous Void Spirits.