The Autons were androids made of plastics and inhabited by the Nestene consciousness.  They are manufactured from a polymer based synthetic resinous product.  They are incredibly strong - they are solid plastic - they contain a blaster disguised within their hands.  The fingers dropped away on a hinged joint, revealing a muzzle that can fire energy bolts capable of destroying or vaporizing on contact.  

The Nestene is a billion-year old collective intelligence who abandoned their physical bodies to become a single entity of pure mind, made of energy.  The Nestene's original shape was a tentacled creature with a large single eye, combining features of both the crab and the octopus.

The Nestene first arrived on Earth in plastic meteors.  (They have a special affinity for plastics, with anything made from plastic by them can be utilized as a weapon). 

They took over the mind of managing director of Autoplastics, Ltd., Hibbert, and used him to manufacture the deadly Autons as well as creating replica's of important government and military figures. 

The first generation of Autons were made to look like store dummies, and were equipped with deadly wrist-blasters.  A more advanced type of Auton were the human-like replicas.  

Their invasion of the Earth failed because the portion of their conscious which had been incorporated on Earth was short circuited by radio signals created by the Third Doctor and Liz Shaw (AAA).  

The Nestene were summoned back to Earth by the Master, who helped them take over the Farrel plastic factory.  During their second invasion, in addition to the deadly, dummy-like Autons, the Nestene also controlled by  short-wave radio, a murderous range of plastic items such as a chair, a doll, a telephone cord, which needed the arrival of more Nestene before they could be activated.

The Autons were also used posing as jolly carnival people, handing out millions of plastic daffodils for free.  The Third Doctor managed to convince the Master that the Nestene would destroy him too, and the Time Lords cooperated to banish them back to outer space before they could fully materialize. (EEE).