Samba is a software package that allows Macs (running some version of OS X) and Unix/Linux machines to see and use Windows networks. It should be installed on any new Mac.
Here's where I weasel out of responsibility: I am NOT a Samba guru. I can barely spell it, though I know what it does and what it's good for. You can go through the posts on this forum to see how to use it in almost any conceiveable way. Of course the search function on these forums, er, doesn't work well (yeah, that's the right words!), but you can just browse through, looking for "Samba" or "Windows network," or the like. That's where I've learned almost everything I know about it.