The Permian period (named after the place where its deposits were first discovered), was the sixth and the last period of the Paleozoic, after the Carboniferous, but before the Triassic. It began roughly 300 +/- 10 MYA and ended approximately 250 +/- 10 MYA, lasting for about 50 +/- 10 million years.
During the Permian mountains were formed in the modern Urals, Western Europe, the Appalachians, etc. The sea levels dropped, creating vast expenses of dry land. The climate varied abrupty, from tropical to dry and hot, to moderate and even to cold. The South Hemisphere even had glaciers.
Among the vertebrates, this was the peak of large mammal-like reptiles, including the gorgonopsids, who died out at the end of the epoch.
The Permian plants too underwent a change: the more basal families got replaced by the first cordaites and conifers.