Search notes:

ORA-00984: column not allowed here

create or replace function tq84_fnc return number as begin
   return 42;
end tq84_fnc;
/

create table tq84_tab (num number, txt varchar(42));

Insert a record into tq84_tab:

insert into tq84_tab values(tq84_fnc, 'hello world');

drop function tq84_fnc;

tq84_fnc is not recognized as an identifier, Oracle throws ORA-00984: column not allowed here:

insert into tq84_tab values(tq84_fnc, 'hello world');

Cleaning up:

drop table tq84_tab;

See also