Many people wonder, if there is a difference between router and modem. Is there any? Because generally speaking, both devices are used to connect to the Internet. It is important to bear in mind, that both of them serve different purposes. In order to connect to the Internet via traditional way (telephone cable) a modem is needed. Router has many other functional features (but you can't connect to the Internet using only a router), for example using a router connected to the Internet you can access the Internet on your laptop using wireless connection. To understand the difference more clearly, I would like to mention some characteristic features of both hardware devices. Let's characterize both router and modem now.
A modem is a device used to translate and transfer the analog signal from the telephone network in order to make it fully understandable for computers and other devices working in a network. When we want to connect to the Internet and obtain data packages, a modem is a fully sufficient device and there are no additional devices needed to establish a proper connection. Interesting fact about modems: they connect with telephone line using a small plug called RJ11 and the signal is transferred further using a RJ45 plug.
Router is an additional device, which is not necessary to connect to the Internet, but only an optional one. Router is a device that understands only computer signal. In simple words, in order to send the signal from a telephone line to a router, it must be previously converted using proper hardware (modem). Router gives you the possibility to connect a couple computers and gather them into a network. A network can be also established only to exchange files, without any Internet connection whatsoever.Credit: http://www.flickr.com/photos/witer/
When it comes to router's network cable connections, it has only RJ45 plugs, one of them (this is the WAN socket) is used to connect to the Internet or any other network, and (typically) 4 sockets (LAN sockets) making it possible to connect four computers or other devices. Most routers have the access point feature included, thanks to which after connecting the device to the Internet, we can connect our mobile devices (like a laptop or a mobile phone) wirelessly to the Internet. It is a quite convenient idea, which eliminates the problem of extensive cables usage. Router, besides serving mentioned purposes, is also a hardware firewall – a device that protects a network (and therefore every device connected to the network) from most of the malware (the sole purpose of this kind of software is to damage the operating system of your device) on the Internet.
So, what is the main difference between router and modem? Modem is mainly used to establish the connection to the Internet using a telephone line and a computer. Router is a supplementary device that is used to provide access to the Internet (or any other network to which it is connected) for many devices in a network, additionally by the means of wireless connection.