Ryloth is a planet that is tidally locked around its sun, so one side is always blazing hot and barren while the other side is cold and dark. These are divided into the Bright Lands and the Night Lands.
The Bright Lands are essentially nothing but barren arid plateaus and sandy desserts with huge rocky spires in some parts and the bones of dead giant creatures of either creatures that actually live there or went extinct centuries ago. The Bright Lands are probably one of the deadliest places in the galaxy, for if the heat doesn't kill you, the vicious predators will, which include giant arthropods. The worst thing about Ryloth are the Heat Storms, literal hurricanes of fire and death. The Bright Lands are so deadly that no Twi'lek has ever trekked through it all alone and survived except a blind twilek child who was later worshiped as divine.
The Night Lands are cold and always dark, but its generally not so bad that its frozen over, at near the equator. Its covered in beautiful glowing crystals and giant bio-luminescent plants and fungi which are the main source of light. Despite the beauty, its full of even more dangerous animals, like the Doashim, which is like a demon crossed with a T-Rex.
Most Twi'leks live along the equator aka the Band of Twilight where night and day meet, hence the whole twilight theme. Mainly in caves or in the sides of mountains or cliffs where the shade is. But even on the equator it can get hot and heatstorms may still happen.
In terms of Government, the planet is pretty divided among the twi'lek tribes but all are ruled by the Clan Council which is made up of elected officials from the big tribes. Also the planet is corrupt as shit and is always selling their own kind as slaves or dealing in drugs because that's all they really have of value.