Hi Jonu,
I have found very limited documentation on the topic of containers for Row store tables
With what ever content is available from the below notes I understand the containers are logical units of storage created by HANA when an active row store table undergoes a change such as creating a new column
they do not seem to exist from SPS10 102.06, SPS11(112) and SPS12 so SAP seems to be getting rid of them due to the known issues documented in below notes
http://service.sap.com/sap/support/notes/2287439
http://service.sap.com/sap/support/notes/2000002
Let me know if you have found this useful
Sunil