The Wikipedia page explains cf. as:
In biological naming conventions, cf. is commonly placed between the genus name name and the species name to describe a specimen that is difficult to identify because of practical difficulties, such as the specimen being poorly preserved. For example, "Barbus cf. holotaenia" implies that the specimen is believed to be Barbus holotaenia but the actual identification cannot be certain.
And from Habitas it becomes apparent that cf. is indeed synonymous to cfr., both being abbreviations for confer:
cf., cfr., confer. : Latin, compare (with)
character, taxonomic : any attribute of a member of a taxon by which
it differs or may differ from a member of a different taxonomy.