Finally, I learnt what these containers are called ^^ They are called 옹기 Onggi. Thanks to a reader, Kevin. I learnt the difference between 장독대 Jang Dok Dae and 옹기 Onggi from Wikipedia.org. There are many things that I don't know about Korean culture and still trying my best to learn about it. Please feel free to correct me if there is any wrong information given in my blog ^^ 감사합니다.