  Fog computing is a recent computational paradigm that was proposed to solve
some weaknesses in cloud-based systems. For this reason, this technology has
been extensively studied by several technology areas. It is still in a maturing
stage, so there is no consensus in academia about its concepts and definitions,
and each area adopts the ones that are convenient for each use case. This
article proposes a definition and a classification relying on a computational
perspective for the fog node, which is a fundamental element in a fog computing
environment. In addition, the main challenges related to the fog node are also
presented.
