[xwiki-users] Confusion on Differences

Hi, I need to understand the differences between some of the modules in XWIKI. What exactly are the differences between Xwiki Enterprise, Xwiki Enterprise Manager and Workspaces. I downloaded Xwiki Enterprise + the the XAR file that came with it. When i installed it i found that it already had the ability to create new spaces. Does that mean that workspaces are already included in the Xwiki Enterprise distribution? Is the Enterprise manager just a way of managing multiple Xwiki enterprise instance? I seem to be a bit confused. When i looked at the manuals it says that enterprise manager allows you to manage multiple wikis but i thought that this was already possible using spaces in the "Xwiki Enterprise" installation that i tried. Thanks