Samba is a suite of programs which work together to allow clients to access to a server's filespace and printers via the SMB (Server Message Block) protocol. Initially written for Unix, Samba now also runs on Netware, OS/2 and VMS. 

In practice, this means that you can redirect disks and printers to Unix disks and printers from Lan Manager clients, Windows for Workgroups 3.11 clients, Windows NT clients, Linux clients and OS/2 clients. There is also a generic Unix client program supplied as part of the suite which allows Unix users to use an ftp-like interface to access filespace and printers on any other SMB servers. This gives the capability for these operating systems to behave much like a LAN Server or Windows NT Server machine, only with added functionality and flexibility designed to make life easier for administrators. 

More Info can be found at:  http://samba.anu.edu.au/samba/