A free software re-implementation of the SMB/CIFS networking protocol, which provides Windows file and print services. Use this tag when your question involves Samba shares, mounts, or printers.

Adapted from the Samba Wikipedia article and the Samba home page:

Samba provides file and print services for various Microsoft Windows clients and can integrate with a Microsoft Windows Server domain, either as a Domain Controller (DC) or as a domain member. As of version 4, it supports Active Directory and Microsoft Windows NT domains.

Samba runs on most Unix, OpenVMS and Unix-like systems, such as Linux, Solaris, AIX and the BSD variants, including Apple's OS X Server, and OS X client (version 10.2 and greater). Samba is standard on nearly all distributions of Linux and is commonly included as a basic system service on other Unix-based operating systems as well. Samba is released under the terms of the GNU General Public License. The name Samba comes from SMB (Server Message Block), the name of the standard protocol used by the Microsoft Windows network file system.

The Samba project is a member of the Software Freedom Conservancy. The goal behind the project is one of removing barriers to interoperability.

For another introduction to Samba, see: Samba: an Introduction