CIFS is microsoft's next version of the SMB File system. The underlying technoligy became well known as a result of the SaMBa project, which allows a Linux server to appear to windows clients as a windows server.
References:
http://samba.org/cifs/docs/what-is-smb.html
http://samba.org/cifs/docs/what-is-smb.html
http://www.microsoft.com/technet/prodtechnol/windows2000serv/reskit/cnet/cnad_arc_endh.mspx?mfr=true
