Dedicated to the 40th Anniversary of the journal; its founder and former editor-in-chief, Professor Karl-Heinz Elster;and Professor Alfred Göpfert, an editorial board member since 1988 in celebration of his 80th birthday)Necessary and sufficient criteria for metric subregularity (or calmness) of set-valued mappings between general metric or Banach spaces are treated in the framework of the theory of error bounds for a special family of extended real-valued functions of two variables. A classification scheme for the general error bound and metric subregularity criteria is presented. The criteria are formulated in terms of several kinds of primal and subdifferential slopes.