SAMBA is a free implementation of CIFS/SMB. The password encryption on Unix and Windows is different, therefore SAMBA must have his own file where the passwords are encrypted either as NT-Hash and/or as LAN-Manager-Hash. LAN-Manager-Hashes are weak and shouldn't be used anymore, NT-Hashes are based on MD4, but no salt is used, therefore users with the same passwords have the same NT-Hash. In this file are also stored machine accounts, if the SAMBA server acts as PDC, such entries ends with $.