Therefore, it is needed a mechanism to connect Layer 2 network to each other, and to determine the path which you want to communicate the opponent. The responsible for that is the Routing, which is the role of Layer 3 .
Summary of Routing
In the figure above, because the router is directly connected to the "192.168.0.0/24", "172.16.0.0/16", (i.e. because it has the IP that belongs to the segment on the interface, ) if coming the packets of these address bands, performs a resolution by ARP, and you can forward the packet to the destination IP.
However, there is no information with respect to "10.0.0.0/8".So you should set the following Static route on the router.
"forward the packets destined to 10.0.0.0/8 to the L3 switch"
This setting is the routing.
Although Layer 2 standard now we encounter is almost ethernet, there are some standard else such as PPP, PPPoE, frame relay, ATM, and HDLC, and you can interconnect routing a these Layer 2 standard.
For studying about Network, I recommend below.