Filer takes the files it's opened with or that are dropped onto it's icon or replicatable dropzone and moves, renames, copies or does all sorts of other things with them according to rules created by the user.
Filer is accompanied by AutoFiler. Instead of working on a set of files provided by the user, it can be started together with Haiku to monitor certain folders and deal with new files appearing there according to the user-defined rules.