The "bin" directory contains the binaries, or scripts, or links to such items, and the "lib" directory contains the shared object files that are common to various Cadence binaries (these are Cadence library functions/code, if you like, like the previous description of shared object and library files in the earlier note [perhaps some of these are not defined by Cadence, but shipped with the tools to ensure that they are present?] ).
If you look at a specific file, you could use the "file" Unix/Linux command to 'test' what type of file it is, for example:
file `cds_root cds_root`/tools/lib/libCdsXmotif.so.2.1
-> <path>/tools/lib/libCdsXmotif.so.2.1: ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV), not stripped
The file command shows that the libCdsXmotif.so.2.1 file is a shared object file.
Does this answer the question?