There are two protocols that can be used to access Windows shares: smb and cifs. The later wants to be the preferred method for accessing remote Windows shares.
The smb:// protocol URI component indicates that the SMB protcol is used to access the resources on the server.
The -t cifs mount command option indicates that the CIFS protocol is to be used (instead of SMB). Linux has both cifs and smbfs as kernel file syste modules.
This article will explain why there are two protocols: http://www.samba.org/cifs/