How to check ORA error or Viewing Errors with the oerr Utility?

Many Oracle products on UNIX have a utility called "oerr" that can be used to aid error investigation. 
The "oerr" utility is a shell script that is located in the ORACLE_HOME/bin directory. "oerr" requires the ORACLE_HOME to be set and two parameters when called: the facility which is the three to four letter code to the left of dash and the error number.