oerr is a shell script that drives ORACLE_HOME/bin/oerr.pl which can be used to translate an error code (of a facility) to a cause and a (hopefully) appropriate action for that that cause.
The facility is identified by the (always(?) three letter) string. For eample for ORA-00600, the facility is ora and the error number is 600.
$ $ORACLE_HOME/bin/oerr ora 600
00600, 00000, "internal error code, arguments: [%s], [%s], [%s], [%s], [%s], [%s], [%s], [%s], [%s], [%s], [%s], [%s]"
// *Cause: This is the generic internal error number for Oracle program
// exceptions. It indicates that a process has encountered a low-level,
// unexpected condition. The first argument is the internal message
// number. This argument and the database version number are critical in
// identifying the root cause and the potential impact to your system.
//
// *Action: Visit My Oracle Support to access the ORA-00600 Lookup tool
// (reference Note 600.1) for more information regarding the specific
// ORA-00600 error encountered.
//
// An Incident has been created for this error in the Automatic
// Diagnostic Repository (ADR). When logging a service request, use
// the Incident Packaging Service (IPS) from the Support Workbench
// or the ADR Command Interpreter (ADRCI) to automatically package the
// relevant trace information (reference My Oracle Support Note 411.1).
//
// The following information should also be gathered to help determine
// the root cause:
// - changes leading up to the error
// - events or unusual circumstances leading up to the error
// - operations attempted prior to the error
// - conditions of the operating system and databases at the time
// of the error
//
// Note: The cause of this message may manifest itself as different
// errors at different times. Be aware of the history of errors that
// occurred before this internal error.