The last bit I understand

My ISP has given me a primary and secondary DNS to use.
However it looks like it is pointing to the routerDefault gateway 192.168.0.1, IP address 192.168.0.3
While looking at the network connection details it also has "Lease Obtained: 31/07/2007 6:57:34 PM Lease Expires: 3/08/2007 6:57:34 PM" what does this mean?