The android is a robotic drone that emulates the human form.
In the Original Series, androids were creations of both the Colonials via the bio-robotics institutes (TOS: "War of the Gods, Part II") and humans originating from Terra, particularly in the form of Hector and Vector, which the Colonials encounter on Paradeen (TOS: "Greetings From Earth").
In Galactica 1980, the Cylons had also perfected androids that were capable of abilities greater than those of mere centurions (1980: "The Night the Cylons Landed").
In the Re-imagined Series, while Cylons had assumed human form, they did so in a more biological fashion, and thus are not considered androids, but cybernetic life-forms.