You'll hear SharePoint veterans talk about and refer to the "12 Hive" or the "60 Hive" regularly. Sometimes we forget that the term is not intrinsically clear to everyone.
The "Hive" concept was coined by Todd Bleeker during the SharePoint 2003 era. His blog is currently called the "12 Hive". So what does it mean?
12 Hive is the location where MOSS 2007 and WSS 3.0 install their files on the file system. The same thing applies to 60 Hive which, as you may guess is the location of SPS 2003 and WSS 2.0 files. They are:
C:\Program Files\Common Files\Microsoft Shared\web server extensions\12
C:\Program Files\Common Files\Microsoft Shared\web server extensions\60