Skaro was home to the Kaleds and Thals. A Nuclear war broke out between the two races. The Kaleds chief scientist Davros created a casing for mutated Kaleds, he called it a ‘Mark 3 travel machine’ later to be known as a Dalek.
The planet itself has very rarely been shown. The image on the left is Skaro getting destroyed in Remembrance of the Daleks. The image on the right is Skaro from the 1996 TV Movie where the Doctor was taking the Masters remains from Skaro back to Gallifrey, the Daleks didn’t feature in this story.
The Daleks were not aware that any Thals survived the war as they could not leave their city. The Daleks coundn’t leave the city as it provided the static electricity they needed to operate. The Thals had evolved and adapted to the radiation. Below are some pictures of the Dalek city, the map on the right charts the history of the Thals.
The second time the Doctor saw Skaro was in The Evil of the Daleks. This time the Daleks were controlled by the Emperor that lived in the middle of the new Dalek city.
The Thals and Kaleds were at war with each other, both lived in seperate domes on Skaro. Davros betrayed the Kaleds as they wouldn’t allow him to complete his Daleks. Davros helped the Thals launch a nuclear attack on the Kaled dome wiping out the Kaled race.
A destroyed and presumably abandoned Skaro was shown briefly in Asylum of the Daleks. A Dalek agent had been sent to capture the Doctor and take him to the Parliament of the Daleks spaceship.