Terrain Feature

A Terrain Feature refers to any dynamically-spawned scenery on a World other than its Points of Interest; Flora in the form of Grass, Flowers, Shrubs, and Trees; Fauna in the form of Critters, Fish, and Insects; Boulders and small Rocks; or — while the World is still being tended towards blooming — Stinkweeds, Withering grass, detritus, and seed plots in need of attention from the Apprentice's Tools. Terrain Features can be walked and/or climbed on, but are otherwise not interactive.

Each World has its own colour of Bedrock which all Terrain Features on that World share, as well as a separate Ground colour which is initially visible over most of a World but, as the Apprentice tends to the World, the Ground is slowly hidden under groundcover Grass, typically of a colour different than the colours of both Bedrock and Ground. Different Biomes have different palettes from which a given World's Bedrock hue can be selected. Bedrock colour and the colours of Boulders and Rocks are usually distinct hues, but can be visually similar or even identical, particularly on Fungi and Nature Worlds.

Terrain Feature types

Bedrock Outcrop refers to any small extrusion of Bedrock above the Ground of a World, sometimes easily mistaken for a Rock.

Bedrock Outcrops and Rock on a Frozen World
Lip, Bedrock Outcrop and Rocks on a Nature World

Climbing Tower refers to a broad, butte-like structure which can, with some effort, be climbed, leading to a level top with a view high above the trees; may possibly appear only on Desert Worlds.
Disc refers to the lowest level of a Bedrock on a World, growing either from another Disc, from a Plateau, or directly from a Seed Planter.
Double-Ramp Structure refers to a raised area which connects to the Ground level of a Disc via two symmetrical smooth Ramps, and may or may not feature a Tunnel in its centre.
Eyelet Tower refers to a large structure, similar in size to a Climbing Tower, but which features a large vertical slit like the eye of a needle.

Climbing Tower on a Desert World
Eyelet Tower above a Pond on a Nature World
Hammerhead Tower on a Desert World
Hammerhead Tower on a Fungi World
Hammerhead Tower on a Princess World

Flair refers to any structure smaller than a Perch which would never be mistaken for a Boulder or Rock, and which represents a Biome present on its World.

Flair on a Fungi World

Ground refers to the base layer of a World, on which Flora is planted, and on which Critters, some Insects, and the Apprentice walk. It is typically but not necessarily distinct in colour from both Bedrock and groundcover Grass colours on a given World, until it is eventually mostly covered by groundcover Grass as the Apprentice cleanses that World of The Withering.
Hammerhead Tower refers to a very large and unclimbable Tower that spreads from a thick column to a broader flat top whose surface is visible only in aerial view when Kazumi is approaching its World.
Lake refers to a large area of shallow water in which Fish can be found; less common than the smaller Pond.

Lake on a Fungi World; at left a giant hollow log Point of Interest provides access to the central island
A Perch and two Leaning Spires on a Desert World
Leaning Spires on a Gross World

Leaning Spire refers to a tall, narrow extrusion of Bedrock which is typically tilted noticeably off vertical, taller than a Perch, but not as tall as a Tower. Leaning Spires on Princess Words may be nearly vertical and may not be climbable.
Ledge refers to a large Platform-like area raised well above the Apprentice's head on columns of varying kinds, and whose upper surface may be reached via a Ramp or a series of Steps.

A Ledge standing out in a Fungi World forest
A Ledge on a Frozen World

Lip refers to the raised area of Bedrock lining most of the edge of a World. A Lip will usually keep the Apprentice from accidentally walking off the edge, but some sections of Lip allow the Apprentice to walk smoothly up onto the rim. Most Ponds and Lakes are enclosed by a Lip, but some are bounded by a giant hollow log Point of Interest instead.
Natural Arch refers to any arch-shaped, bridge-like Bedrock structure which the Apprentice may pass under (but not to Tunnels, which are longer than they are wide, nor to Overhangs, which open only on one side).
Overhang refers to a Bedrock extrusion resembling a broad-mouthed but shallow Cave.

A Natural Arch between stacked Platforms and a Battery-Operated Chest Dispenser on a Desert World
A Natural Arch surrounded by Leaning Spires on a Princess World
A Natural Arch atop a Lip-less Double-Ramp Structure on a Frozen World
A Perch, occupied by Kazumi, beside an Overhang on a Nature World
View from inside a Princess World Overhang; beige Bedrock, pink Ground and green Grass colours show on walls

Perch refers to any structure on which the Apprentice's mount may perch; this may or may not be climbable by the Apprentice.
Plateau refers to a large area raised above the Ground, which may be reachable by climbing an incline, Steps, or footholds, or may only be accessible via a Bumbershooter from an adjacent Plateau or Disc.
Platform refers to an area raised above the Ground of a Disc. Platforms often stack, and in some Biomes it's possible to walk smoothly up such stacks (Fungi, Nature) while in others even the lowest Platform requires a jump to access (Desert, Princess); see also Ledge.

A large Platform on a Desert World, with the Ground rising to provide the Apprentice an incline to walk up at left
A stack of small Platforms on a Fungi World; a Shrub grows from the middle Platform
Small Platforms on a Princess World, shaped like crenellated tower-tops, interspersed with conical-topped Flair

Pond refers to a small area of shallow water in which Fish can be found; more common than the larger Lake. Some smaller Ponds feature a central island just large enough for a single Tree.
Pseudo-Boulder refers to any Terrain Feature which resembles a Boulder in shape and size but which cannot be cracked with the Apprentice's Mallet.
Ramp can refer to an incline directly connecting two Discs at different heights, or to an incline providing access to a Ledge or Plateau. See also Double-Ramp Structure and Spiral-Ramp Plateau.

Ramp leading to a Plateau, leading in turn to another Disc
Spiraled Perch atop a Spiral-Ramp Plateau on a Nature World
Spiral-Ramp Plateau on a bloomed Nature World

Spiral-Ramp Plateau refers to a Plateau accessed via a ramp spiraling up its side, which can typically be walked up smoothly at its outer edge but which has small lips on the inside (plateau side) edge of the ramp sufficient to force the Apprentice to either jump up or move toward the outside edge of the ramp in order to ascend.
Spiraled Perch refers to a Perch which is at least partly encircled by a Ramp or Steps leading partway up the central column.

Spiraled Perch on a Nature World
Small Steps on a Desert World
Large Steps on a Nature World

Steps refers to any series of Bedrock extrusions of different heights which go upwards stepwise but which the Apprentice must jump up rather than walk up; these may be of Platform height but too sharply angled to allow a smooth climb, or the individual steps may be taller such that no amount of rounding would allow the Apprentice to walk up.
Tower refers to any of several types of large structure, usually not climbable or used as a Perch; see Climbing Tower, Eyelet Tower, Hammerhead Tower.
Tunnel can refer to one of two types of tunnels found on worlds: regular Tunnels are found underneath some Double-Ramp Structures (and may either lead to another Disc, or open out onto the edge of the Disc with no Lip to keep the Apprentice from falling off — a "Tunnel to Nowhere"), whereas a Large Tunnel occupies the space of an entire Disc and always connects two other Discs. See also Natural Arch.

Mouth of a Large Tunnel on a Princess World
Hammerhead Tower and Double-Ramp Structure with "Tunnel to Nowhere" on an Ice World
Aerial view of a "Tunnel to Nowhere" on a Gross World

Note that this listing is not exhaustive and there are Terrain Features remaining to be discovered!