What is the difference between procedure and function

A procedure is a collection of PL/SQL code named, defined by user and usually stored in the database.

A function is the same like procedure except that it must return a value, using the keyword RETURN.

Procedure Example

CREATE OR REPLACE PROCEDURE raise_price
(	p_id    IN products.product_id%Type,
	p_percent   IN NUMBER
) IS
BEGIN
	UPDATE products 
	SET price= price*(1+p_percent/100)
	WHERE product_id = p_id;
END raise_price;

Begin
	raise_price(300,10);
End;

Function Example

CREATE OR REPLACE FUNCTION Get_Price
(p_id products.product_id%Type)
RETURN NUMBER
IS
	v_price products.price%TYPE :=0;
BEGIN
	SELECT price
	INTO v_price
	FROM products
	WHERE product_id = p_id;
RETURN v_price;
END Get_Price;

Begin
dbms_output.put_line(Get_Price(300));      
End;