  In this article we focus on kinetic equations for gas mixtures since in
applications one often has to deal with mixtures instead of a single gas. In
particular we consider an approximation of the Boltzmann equation, the
Bathnagar-Gross-Krook (BGK) equation. This equation is used in many
applications because it is very efficient in numerical simulations. In this
article, we recall a general BGK equation for gas mixtures which has free
parameters. Specific choices of these free parameters lead to special cases in
the literature. For this model, we provide an overview concerning modelling,
theoretical results and numerics.
