What is the difference between user-defined and pre-defined PLSQL exception?

Pre-defined PL/SQL exceptions are built into the Oracle database and represent common error conditions, such as NO_DATA_FOUND or TOO_MANY_ROWS. In contrast, user-defined exceptions are custom exceptions that developers create to handle specific error conditions relevant to their applications. While pre-defined exceptions offer standard error handling mechanisms, user-defined exceptions provide flexibility for addressing unique business logic and conditions. This distinction allows for more tailored error management in PL/SQL programs.