Below is the description of all. Have a look!
SQL> show parameter BACKGROUND_DUMP_DEST
This shows the bdump directory you were referring to in your question. This is a directory where debugging trace files for the background processes (LGWR, DBWn, and so on) are written.
SQL> show parameter USER_DUMP_DEST
This specifies the pathname for a directory where debugging trace files will be written on behalf of a user process.
The dpdump directory has files created by the data pump export/import utility.
The adump directory is the area where auditing trace files are stored.
CDUMP is specifying the core dump directory where all OS error logs (core dump files) will be placed.