Parameter & Keyword Description:

function_name:

The user-defined function is identifying by that keyword.

parameter_name:

This identifies the formal parameter that is a variable declared in a function specification and referenced in the function body.

IN, OUT, IN OUT:

These parameter modes define the behavior of the formal parameters. An IN parameter pass the values to the subprogram being called. The OUT parameter returns values to the caller of the subprogram. An IN OUT parameter pass the initial values to the subprogram being called and return the updated values to the caller.

NOCOPY:

This is a compiler hint and not directive, that allows the PL/SQL compiler to pass the OUT and IN OUT parameters by reference rather than by the value.

Datatype:

This is merely a type specifier.

: = | DEFAULT:

This keyword or operator allows you to initialize the IN parameters to the default values.

Expression:

This is a randomly complex combination of constants, variables, literals, operators, & function calls. The simplest expression consists of a single variable. When the declaration is explained, the value of expression is assigned to the parameter. The value and the parameter should have the compatible datatypes.

RETURN:

This keyword introduces the RETURN clause that specifies the datatype of the result value. 

type_definition:

This user-defined datatype is specified by this keyword.

item_declaration:

A program object is declared by this keyword.

function_declaration

The function n is declared by this construct.

procedure_declaration:

The procedure is declared by this construct.

exception_handler:

This construct relates an exception with a series of statements that is executed when that exception is raised.