Stands for "Server Message Block." SMB is a network protocol used by Windows-based computers that allows systems within the same network to share files. It allows computers connected to the same network or domain to access files from other local computers as easily as if they were on the computer's local hard drive.
Not only does SMB allow computers to share files, but it also enables computers to share printers and even serial ports from other computers within the network. For example, a computer connected to a Windows network could print a document on a printer connected to another computer on the network, as long as both machines support the SMB protocol.
Though SMB was originally developed for Windows, it can also be used by other platforms, including Unix and Mac OS X, using a software implementation called Samba. By using Samba instructions, Mac, Windows, and Unix computers can share the same files, folders, and printers. This is great for those Windows-based office networks where there is a graphic designer who refuses to use anything but a Mac and a tech guy who does everything on his Linux machine.