A long time ago in galaxy far, far away... on a planet called Gallifrey there lived an animal. A time beast. Evolution had given the time beast a defence mechanism. It was able to evade predators by adjusting the flow of time. When a predator confronted a time beast it would find that somehow time speeded up, just slightly, while from the time beast's perspective time slowed down slightly. Thus a time beast could almost always evade predation. After millions of years the time beast evolved into the race of time lords.
Meanwhile, in another galaxy, was a planet called Skaro where a race of people called the Kaleds were at war with the Thalls. These two races were of the same species but had been locked in bitter race hatred and war for many years. In the kaled cities houses were cleaned by a robot device called a dalek, a pepperpot shaped mechanism which was able to unblock sinks and exterminate small animals. It was a stupid mechanical utility with no real artificial intelligence, just a bunch of easily reprogrammable subroutines. It would trundle around the city exterminating pests and fixing problems with the plumbing. A different version of the same technology was available minus the rotating top part and with a built-in seat and control panel. This version of the dalek machine could function as wheelchair for the disabled.
When the war with the Thalls went nuclear civilisation was nearly destroyed and wastelands were created where mutated versions of Kaled humanoids wandered and continued to mutate. A scientist named Dave Ross (oops! sorry, Davros) who was himself wheelchair bound adapted the simple dalek machine into a travel machine for a new kind of Kaled. davros's theory was that, instead of stopping the mutations the Kaled race should follow the trend to it's ultimate form. He was living the dream of all scientists: stark staring mad but with adequate funding.
Eventually a member of the timelord race visited Skaro and told the Daleks how to leave Skaro, travel through space and time, conquer Earth, destroy Gallifrey and rule the universe. Ironically this same timelord was the only survivor of of the destruction he had wrought by alerting the Daleks to the fact that they were not alone in the universe.
More about him later.