LIB vs LIBPATH (environment variables, difference for MS Visual C/C++)?

I've been working on some build scripts, and this is bugging me. I want to be sure that we're independent of environment settings, but in order to be sure of that I feel a need to understand how/where the settings are used by the tools. The Visual Studio command prompt and/or vcvarsall.bat file set up two distinct environment variables: LIB and LIBPATH. The values are different, but partially overlapping. Here are the values from my system: ``` LIB=C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\LIB;C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\ATLMFC\LIB;C:\Program Files (x86)\Windows Kits\8.0\lib\win8\um\x86; LIBPATH=C:\Windows\Microsoft.NET\Framework\v4.0.30319;C:\Windows\Microsoft.NET\Framework\v3.5;C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\LIB;C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\ATLMFC\LIB;C:\Program Files (x86)\Windows Kits\8.0\References\CommonConfiguration\Neutral;\Microsoft.VCLibs\11.0\References\CommonConfiguration\neutral; ``` I'd just like to understand the rationale for having two different variables -- a little more than the obvious fact that LIBPATH brings in more libs. I've tried looking it up, but I haven't found a clear definition of when each is used by the linker and/or the dev environment.