The questions you asked are answered by the editing guidelines, which of course you’ve read before making any modifications:
panda3d.org/manual/index.php/Talk:Main_page
As for the libraries, to the best of my knowledge:
avcodec-53.dll - Part of ffmpeg, linked into the core, so don't remove it
avdevice-53.dll - Part of ffmpeg. We don't use this one.
avfilter-2.dll - Same, we don't use this one either.
avformat-53.dll - Part of ffmpeg, linked into the core, so don't remove it
avutil-51.dll - Part of ffmpeg, linked into the core, don't remove
cg.dll - Cg runtime
cgD3D10.dll - Cg+DX10, you can remove this
cgD3D11.dll - You can remove this, too
cgD3D8.dll - Same
cgD3D9.dll - Cg for DirectX 9
cgGL.dll - Cg for OpenGL
cv100.dll - Part of OpenCV, linked into the p3vision module
cvaux100.dll - Same
cvcam100.dll - Same
cxcore100.dll - Same
cxts001.dll - I have no idea.
d3dx9_37.dll - Part of DirectX 9 runtime
fmodex.dll - FMOD EX sound system
fmodexL.dll - Same, but I don't think we use this one
highgui100.dll - Part of OpenCV, linked into p3vision
libguide40.dll - I don't remember. Maya? Or OpenCV?
libp3direct.dll - Contains various modules like the interval system
libp3dtool.dll - Core of Panda, don't remove
libp3dtoolconfig.dll - Part of Panda's core
libp3fmod_audio.dll - Panda's FMOD module.
libp3framework.dll - Not 100% sure if Python users need this one
libp3glstuff.dll - Important for OpenGL stuff.
libp3mayaloader2008.dll- obvious
libp3mayaloader2009.dll- "
libp3mayaloader2010.dll- "
libp3mayaloader2011.dll- "
libp3mayaloader2012.dll- "
libp3mayaloader6.dll - "
libp3mayaloader65.dll - "
libp3mayaloader7.dll - "
libp3mayaloader8.dll - "
libp3mayaloader85.dll - "
libp3openal_audio.dll - OpenAL audio library wrapper
libp3ptloader.dll - Allows you to load .x, ,dxf, etc using loader.loadModel
libp3pystub.dll - Only needed for the binary tools to run, not the libraries
libp3vision.dll - Webcam stuff, and OpenCV integration
libp3windisplay.dll - Needed by display modules on Windows
libpanda.dll - Contains the gist of the Panda3D stuff
libpandaai.dll - PandaAI
libpandabullet.dll - Bullet physics integration
libpandadx8.dll - Panda3D DirectX 8 renderer
libpandadx9.dll - Panda3D DirectX 9 renderer
libpandaegg.dll - Egg loader, you can remove this if you don't load eggs
libpandaexpress.dll - Part of Panda's core
libpandafx.dll - Some esoteric stuff like special lenses
libpandagl.dll - Panda3d OpenGL renderer
libpandaode.dll - ODE physics engine wrapper
libpandaphysics.dll - Panda3D's internal physics engine
libpandaphysx.dll - PhysX physics engine integration
libpandaskel.dll - Example module, you don't need this.
libpandatiff.dll - Loads tiff images, I think it's linked into the core
libtinydisplay.dll - Panda3D software renderer
mfc90.dll - Microsoft Foundation Class
mfc90u.dll - "
mfcm90.dll - "
mfcm90u.dll - "
ml100.dll - OpenCV stuff again
msvcm80.dll - MS standard library
msvcm90.dll - "
msvcp80.dll - "
msvcp90.dll - "
msvcr80.dll - "
msvcr90.dll - "
msvcrt.dll - "
ode.dll - ODE physics engine
OpenAL32.dll - OpenAL audio library
postproc-51.dll - An ffmpeg library we don't use
python2X.dll - Just a copy snatched from the Python installation
swscale-2.dll - Part of ffmpeg, we do use this