There are three types of parameters in PL/SQL which are as follows:
IN : IN parameters allow you to send values to the procedure that is being called, and they can be set to default values. They behave as constants and cannot be changed.
OUT : OUT arguments must be mentioned because they return a value to the caller. These are uninitialized variables that can’t be used in expressions.
IN OUT : IN OUT parameters send starting values to a procedure and then return updated values to the caller. These parameters should be treated as initialized variables and given a value.
