  We present the theory of linear rank-metric codes from the point of view of
their fundamental parameters. These are: the minimum rank distance, the rank
distribution, the maximum rank, the covering radius, and the field size. The
focus of this chapter is on the interplay among these parameters and on their
significance for the code's (combinatorial) structure. The results covered in
this chapter span from the theory of optimal codes and anticodes to very recent
developments on the asymptotic density of MRD codes.
