Warning:Wikipedia contants spoilers!
Geography
It is the sole planet orbiting its star and has almost no metals. Being on the fringe of the galaxy, there are almost no stars in the sky. The capital of Terminus is Terminus City. Terminus City houses the Seldon time chamber, where messages recorded by Hari Seldon before his death are played at the beginning of Seldon Crises.
Prior to human occupation, there was some life on Terminus. However, once humans arrived (along with their supporting species), these native life forms were crowded out and become extinct.
History
With the Galactic Empire in fatal decline, Hari Seldon, inventor of the science of psychohistory, creates a plan to shorten time to the rise of a New Empire from 30,000 years to 1,000 years.
He asks the chief librarian of the Library of Trantor to undertake a search to find a suitable planet, according to Seldon's criteria. The librarian, following a lengthy search, finds Terminus, which at that point was uninhabited.
Seldon convinces the Empire (in particular, the totalitarian Commission of Public Safety) to set up a colony on Terminus with 100,000 scientists, whose ostensible purpose it will be to publish an Encyclopedia Galactica. In actuality, their job will be to preserve science and technology to speed the time until the rise of the next empire.