The source and destination ip address one is used when there is another network that you specifically know about, and need to route traffic to that network. This is used if you are not using a routing protocol sucah as RIP, EIGRP or OSPF. The main problems are that it is not flexible, so if there are changes in the network, you may need to change all the static routes.
The route with eight zeros, and the destination, is called the default route, and is used to route everything that we don’t have a specific route for the destination.
On most smaller networks we know about our internal networks, and if there are only a few of these, then static routes are fine. The default route (8 zeros) is used for the connection to the Internet, as this is where everything else is located.
I hope that helps.