A factorette is a unit of composability of a larger Software factory that extends another software factory.
A factorette typically (but not exclusively) presents a single view point (called 'A Single View-Point Factory'). That is, a factory that addresses at least one concern/technology/pattern/aspect of a larger solution/architecture etc.
Factorettes enables modularization or Composability of a Software factory.
References
Factorette Wikipedia(Text) CC BY-SA