What are routers? Why we need them?

A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet. Data sent through the internet, such as a web page or email, is in the form of data packets. A packet is typically forwarded from one router to another router through the networks that constitute an internetwork until it reaches its destination node.
Need of routers :

Routers let multiple computers share a common Internet connection from your ISP (Internet Service Provider). This applies to cable, DSL input, or by 3G mobile using USB Dongle.
Routers support NAT, meaning Network Address Translation. This means that the Public IP address is assigned to the router, and not to any of the PC's on the Local ( LAN ) side of the router.
A computer connected directly to the ISP cable connection is subject to attack. The presence of a router, improves security.
Some routers support advanced security such as VPN, which allow business customers at home,to safely log in to their business networks remotely.