Pern as a World
Courtesy of Wikipedia, mostly.
Pern was explored and cleared for colonization by an EEC team, two hundred years before the actual colonization commenced. They labeled the planet with the acronym: Parallel Earth, Resources Negligible (i.e., insufficient to support interstellar commercial investment).
Pern was colonized by settlers originally from Earth, First Base on the Moon, and the colony at Alpha Centauri. The 6,000 colonists wanted to return to an agrarian society with a low level of technology so badly that they were prepared to take a fifteen-year one-way journey to an isolated part of the galaxy.
Less than a decade after the first colony was established, the settlers discovered that their chosen planet was subject to periodic attack from space by the destructive Thread, a spaceborne spore that destroys organic substances on contact.
A small indigenous lifeform, the Fire-Lizard, was discovered with remarkable adaptations against Thread: flight, teleportation, limited telepathy, and the ability to chew phosphine rock and generate bursts of flame.
Kitti Ping genetically "upgraded" these into full-sized flame-breathing telepathic dragons, who were able to sear the Thread before it could fall to the ground. Dragonriders became a vitally important and highly respected profession, especially after a mass migration to the northern continent, where they lived in Weyrs, and, as time progressed, the settlers forgot their Terran origins.
Pern has two moons, Belior and Timor. The Rukbat system also contains two asteroid belts and an Oort cloud. The Oort cloud and a rogue "sixth" planet, the Red Star, plays a major role in the series, as it is the source of Thread.
There are several types of plants which are edible to humans, including the redfruit tree, which produces a red, plum-like fruit, and the klah tree, whose bark is infused like coffee into a stimulant beverage reminiscent of chocolate, coffee and cinnamon. Native medicinal plants include dragon's tongue, which produces a gel similar to aloe; the Needlethorn, whose hollow thorns can be used as hypodermic needles; Numbweed, a strong analgesic plant that is made into a cream after boiling it in large pots for 3 days that numbs small wounds completely, and dulls larger wounds; and Fellis, which produces a juice used as a soporific drug. Terran origin plants make up most food, including grains and fruit trees.
Native Pernese vertebrates have a body-structure with six limbs. Flying creatures, such as the fire-lizards and wherries (carnivorous creatures not dissimilar to large birds), have two wings and four legs. Ground-bound creatures like most tunnelsnakes have six legs, which may include specialized digging feet or hunting claws. Wherries are edible, and have been domesticated for food; some tunnelsnakes are edible, but they are primarily considered an, occasionally dangerous, pest animal. The most common food fish is the packtail, whose tail is incredibly sharp and infective.
Terran origin animals include domestic canines and felines kept for pest control; herd and milk beasts (bovines, ovines, caprines) kept for food, skins and milk; runners, a breed of horses used in races and non-dragonback messaging; and packbeasts used for hauling or plowing.