Oracle Server Manager User's Guide
DESCRIBE
Purpose
Describe a function, package, package body, procedure, table, or view.
Prerequisites
You must be currently connected to a database.
Syntax
DESCRIBE command ::=

where:
Usage Notes
Procedures inside of packages cannot be described with this command.
Example
A command like
DESCRIBE PROCEDURE scott.addemp
produces output similar to the following example:
PROCEDURE SCOTT.ADDEMP (EMPNO INTEGER, ENAME VARCHAR2, SAL NUMBER(9,2))