The most common terrain is normal terrain, the map usually starts with normal terrain only. The other terrain types are exceptions and only appear in certain maps, themes and gameplay events.
Note there is no direct visual distinction between terrain types as such. There may or may not be visual aids on maps. In normal gameplay, however, it should be pretty clear to recognize icy and bouncy terrain.
The normal terrain can be destroyed by weapons, utilities and other means.
Hedgehogs and most projectiles and objects will bounce off the bouncy terrain without taking fall damage. A collision with bouncy terrain does not count as an impact and will therefore not trigger explosions.
Using Rubber is a natural way to create a bouncy terrain.
Portals from the Portable Portal Device do not work on bouncy terrain.
Most things will bounce but a few things do not, so here is an incomplete list of things which will—surprisingly—not bounce and instead take damage on collision:
Icy terrain is very slippery and any hedgehog will usually slide off slopes easily, so it can be quite dangerous to walk on. But there is a way to get across icy terrain safely: As long as you hold the Precise key, your hedgehog will not slide away. This will also slow down the slide if it is already sliding.
In the Snow and Christmas themes, all bridges and Constructions will be icy terrain.
This terrain can not be destroyed by most weapons, flames and explosions. These weapons and utilities are still able to destroy this terrain:
This terrain type is only used when the game modifier “indestructible terrain” is enabled. It then turns the entire terrain into (at least) semi-indestructible terrain.
This terrain type is a somewhat special case here, since the only way to get it is by using this game modifier. It is not possible for themes and maps to have this terrain type as such or only have a part of the terrain which is semi-indestructible.
Fully indestructible terrain
This terrain can not be destroyed by any means. If you try to dig through, you will simply be stopped by the terrain. This terrain type is a rare sight in normal gameplay and can probably only be seen in styles like TechRacer or in special maps.
The game modifier “indestructible terrain” has no effect on fully indestructible terrain. Fully indestructible terrain will stay this way and is not “degraded” into semi-indestructible terrain.
It is also possible for terrain to combine the properties of the terrain types above. For example, terrain can be both icy and bouncy. This could be achieved by using a freezer on rubber.