Overview

Kerbin is a rocky planet that is slightly smaller than Earth, with somewhat equivalent gravity. It is around 12500 kilometres in diameter. It takes at 18 hours to spin around its axis relative to it's star, Kerbol, and completes 1 orbit around it every 319.5 earth days, at an average distance of around 0.95 astronomical units.  That equates to around 426 local days. Kerbin is orbited by 2 moons, Mun and Minmus. The Mun is the closest moon, and it completes an orbit once every 21 Kerbin days. It is comprised of grey rocks, and is Kerbin's analogue for Earth's Moon. Minmus, is further out, taking around 47 Kerbin days to complete an orbit around Kerbin.

Kerbin is perhaps the grassiest planet in the known universe, with the planet being almost covered with grass-like vegetation. It does, however, have a massive desert to the west of the temperate continent of Kafrica, and a large tropical rainforest encompassing the oriental Loveheart Ocean, named so for its heart-like shape. The planet in general has a fairly mild climate. Kerbin's axial tilt is around 20 degrees, which means that the planet has less seasonal variation than earth.

Description in KSP

A unique world, Kerbin has flat plains, soaring mountains and wide, blue oceans. Home to the Kerbals, it has just the right conditions to support a vast, seemingly undepletable population of the eager green creatures.

Reaching a stable orbit around Kerbin is one of the first things budding space programs strive for. It is said that those who can get their ship into orbit are halfway to anywhere. 

Description in KSP2

Even as rockets and probes escape its atmosphere for deep space exploration, there is still much appreciate about this vibrant world. Its vast oceans, deserts, forests, and plains coat the surface in lively beauty. Its moons, Mun and Minmus, swirl silently above it. Kerbalkind is fortunate to call this pale blue planet their home.