Water help

[David075]

While changing the parts in a leaking tap the other day I decided to have a close look at my water supply when I had a look at the water tank in the loft I spotted that its two tanks that are there both labelled 227 ltrs im just wondering if anybody can tell anything more about this system as don't know much about how it works ? also when I turned off the main to fix tap in kitchen the water stopped straight away but the bathroom still had water , from one or both of the tanks I presume .