In Kerbal Space Program a biome is a geographic area on the surface of a celestial body typically corresponding with types of geology like mountains or craters. This is in contrast to the real meaning of the term in which biomes are biotic communities in contiguous areas with similar climatic conditions and organism populations.
The results of science activities often differ when performed in different biomes, and thus provide more opportunities to earn Science Points in Career Mode to research further along the technology tree. In Sandbox, even the text descriptions from experiments are unavailable, rendering biomes unimportant. For details and tips on how to get as much Science as possible from exploring biomes (and where to find water in a Mountain biome, for example), see the Science Tutorial.
Areas belonging to a biome may be geographically separate, but they're not considered different areas. For example, after performing an EVA Report at Kerbin's north polar IceCap biome, performing one from the southern IceCap gives the same results (and Science Points) as if it had been performed a second time in the northern IceCap.
With version 0.90 biomes were added to all celestial bodies which have a solid surface, which excepts Jool and the Sun. Before that only the Kerbin system - Kerbin, Mun and Minmus - had biomes. Jool's moon Laythe and the planet Eve have bodies of water and science activities performed in them stated as being from "Laythe's oceans" and "Eve's oceans". However, this was just the effect of the situation "SrfSplashed" for a splashdown versus the usual "SrfLanded" surface landing.
Moho has 12 biomes. It is one of three bodies (the other being Kerbin and Ike) that have their own North and South Pole biomes. It is dotted with Minor Craters and features four distinct Lowland Biomes.
Eve has 15 biomes with their own science to be collected. It's main features are a large Explodium Sea with some scattered Islands and Shallow areas as well as a Main Continent and Poles. Within the Continent lie three large bodies of liquid, one being a Crater Lake. There are also areas covered with Impact Ejecta.
With only 3 biomes, the moon of Eve, called Gilly, has the fewest number of biomes.
The planet Kerbin has 11 biomes, plus a large number of surface-only “location biomes” comprising Kerbal Space Center. Roughly 60% Kerbin's surface is Water biome. Grasslands and Highlands biomes cover most of the land area. Along with Moho and Ike it has distinct polar biomes.
Kerbin is the only celestial body with location biomes: the grounds of KSC and the many structures it is composed of. Each count as a biome only with experiments performed on the surface. KSC is within a Shores biome, so experiments while flying at any altitude over the KSC count as Shores. However, it is possible to get an "EVA Report while flying over" the area, either while jumping, grabbing a ladder on a craft, or sitting on a EAS-1 External Command Seat.
The biggest moon of Kerbin, called the Mun, has a total of 17 biomes, 7 of which are uniquely named major craters. The Mun has the largest amount of biomes in the Kerbol System. Most of the surface area belongs to the Midlands biome followed by the Highlands. Canyon biomes extend off a few major craters.
The moon of Kerbin, called Minmus, has a total of 9 biomes. The most distinctive quality of Minmus's biomes is the variety of Flats, which in-game text describe as “lake beds”. They are almost perfectly flat and may represent salt flats. Roughly two-thirds of the surface area is irregular terrain transitioning between Highlands, Midlands, and Lowlands with Slopes in-between.
The planet Duna has 14 Biomes. Within the generic mix of Low-, Mid- and Highlands lie various Basins and Canyons with some scattered craters. The most dominant feature is the Midland Sea, which spans half the Planet. The Poles also include separate Highlands and Craters.
The moon of Duna, called Ike, has 8 biomes. It is one of three bodies (the other being Moho and Kerbin) that has their own North and South Pole biome.
The planet Dres has 8 biomes.
The planet Jool has no biomes, since it is a gas giant and therefore landing on its surface is not possible.
The first moon of Jool, called Laythe, has 10 biomes. Laythe consists primarily of a huge ocean, called The Sagen Sea, with another ocean called the Degrasse Sea and some small Peaks, Dunes and Shores biomes. It also has a Poles biome.
The second moon of Jool, called Vall, has 9 biomes. It has mostly large Lowlands broken up by Midlands and Highlands with some high Mountains in between. There are four distinct Basins and Poles available as well.
The third moon of Jool, called Tylo, has 9 biomes. It mostly consists of generic Low-, Mid- and Highlands with some Mara and Minor Craters scattered in between. There are four distinct Craters. Previously three of these Craters were simply named Major Crater, the reason for this oddity not being known.
The fourth moon of Jool, called Bop, has 5 biomes.
The fifth moon of Jool, called Pol, has 4 biomes.
The planet Eeloo has a total of 11 biomes.