What is the difference in TFS 2010 between a source server and symbol server?

I have read a couple of posts for instance... http://blogs.msdn.com/b/adamroot/archive/2009/06/17/source-server-and-symbol-server-features-in-team-foundation-server-2010-beta-1.aspx

http://blogs.msdn.com/b/jimlamb/archive/2009/06/15/symbol-and-source-server-in-tfs-2010.aspx

From what I have read these are both useful server applications to setup for better debugging support when dealing with older versions of applications that require analysis.

In the first link the msdn blogger mentions that while both are useful they are seperate and don't depend on each other. Why would I want one and not the other? Do they perform two distinctly different tasks or do they overlap?

happy for others to edit Q or ask me to edit if this isn't clear enough.

Solution

Most of the time, you want both. They do not overlap. In short

Symbol server gives you function names and line numbers
Source server gives you the source at a point in time

But there are debugging scenarioss when sources are not available, like for the Windows DLL and executables for example. So it is usefull to have them separate, even if it comes with it's own agravation.

In Microsoft's Debugging tools for windows, there is a command symfix (or symfix+) that adds Microsoft's symbol server to your configuration automaticaly.