This article is from the Chemistry FAQ, by Bruce Hamilton B.Hamilton@irl.cri.nz with numerous contributions by others.
Naphtha is a refined light distillate fraction, usually boiling below 250C,
but often with a fairly wide boiling range. Gasoline and kerosine are the
most well-known, but there are a whole range of special-purpose hydrocarbon
fractions that can be described as naphtha. The petroleum refining industry
calls the 0-100C fraction from the distillation of crude oil "light virgin
naphtha" and the 100-200C fraction " heavy virgin naphtha". The product
stream from the fluid catalytic cracker is often split into three fractions,
<105C = "light FCC naphtha", 105-160C = "intermediate FCC naphtha" and
160-200C "heavy FCC naphtha".