Android 19 is a large android with completely white skin and was created by Dr. Gero in order to kill Son Goku as revenge for destroying the Red Ribbon Army. He first appeared alongside Android 20 on an island 9 kilometers southwest of South City where they both started wreaking havoc before being intercepted by Goku and his allies, who had been warned of their appearance by Trunks. He has the ability to absorb people's energy through his hands to give himself the upper hand in combat.

In "Dragon Ball Full Color: Artificial Humans & Cell Arc Volume #03," Akira Toriyama revealed that: "The model for No. 19 was a doll that was displayed in the command center of an enemy base. Way back when, Dr. Gero took it back with him as a war trophy."

(Sources: Wikipedia, Kanzenshuu)