NVL and NVL2 in Oracle

SQL> WITH ADDRESS
  2       AS (SELECT 10 AS ID,
  3                  'BANGALORE' AS ADDRESS1,
  4                  'HYDERABAD' AS ADDRESS2,
  5                  'CHENNAI' AS ADDRESS3
  6             FROM DUAL
  7           UNION ALL
  8           SELECT 20 AS ID,
  9                  '' AS ADDRESS1,
 10                  'HYDERABAD' AS ADDRESS2,
 11                  'CHENNAI' AS ADDRESS3
 12             FROM DUAL)
 13  SELECT ID,
 14         ADDRESS1,
 15         ADDRESS2,
 16         ADDRESS3,
 17         NVL (ADDRESS1, ADDRESS2) AS NVL,
 18         NVL2 (ADDRESS1, ADDRESS2, ADDRESS3) AS NVL2
 19    FROM ADDRESS;

        ID ADDRESS1  ADDRESS2  ADDRESS NVL       NVL2
---------- --------- --------- ------- --------- ---------
        10 BANGALORE HYDERABAD CHENNAI BANGALORE HYDERABAD
        20           HYDERABAD CHENNAI HYDERABAD CHENNAI

SQL>