Router Benefits

• Routers by default breakup broadcast domain and it is helps to connect to WAN (Wide-Area-Network),
• Routers are using something called a serial interface for WAN Connection (V.35 physical interface on a cisco router)

Why we need to breakup broadcast domain?

Breaking up a broadcast domain is very important because now you have to send a "Network Broadcast" to a another host on a network, Some how you have sent the network broadcast to the host in other words every hosts in a network read and process the particular network broadcast message. 

• Routers are not only breaking up the broadcast domain but also collision domain as well. 

2 Main advantages of using a router

• They don't forward broadcast domain by default. 
• They can filter the network based on Layer 3 (We will talk about Layer functions and OSI layers later)

4 Functions of a Router

1. Packet Switching - Router also defined as "layer 3 Switches". use for logical addressing that's why we called as packet switching.
2. Packet Filtering and Internetworking - Router also packet filtering to using access list.when two or more routers in a networks together use logical addressing  (IP -IPV4 Or IPV6 ) What is called Internetwork
3. Path Selection - Routers are using a Routing table (map of the internetwork) to make path selections and forward packets to remote network. 

( I just gave you 3 on the above list but in the 2nd option you'l lsee packet filtering and internetworking, i just combined two options as one)

Maybe You have a Question Like This - How much broadcast needs to a network? 

Actually this is question when i asked in forums when i'm newbie still i'm newbie- I'm taking CCENT so this blog is very helpful to provide the useful notes for your cert exams indeed. so this is the answer,

Always keep in mind - Broadcast domains on how you segmented a network..