The library directory contains some usefull .rt files. You should not open this files, you must include them int your scene with "Insert|Library|*" or with "Insert|File RT" command. They are organized in subdirectory:
field standard field objects ( described below )
material common materials
param common sets of rendering variables
In material subdirectory:
glass green glass
In material subdirectory:
fast faster raytracing rendering
hquality high quality rendering