A Router is a network device that sends data packets across networks. Routers connect 2 networks together. Whether its two LANs, WANs or both. For example, a router in your home or office connects your LAN to the internet. Here is another example; there is the Widget Company. They have two offices, one in Los Angeles and one in New York City. A router can be used to connect the two office networks together. Routers vary in cost and abilities depending on your needs.
A Switch builds or creates networks. In most of today’s networks, switches are what connect servers, computers and printers in the same network (the accounting floor for example), allowing them to effectively communicate with each other. Switches and routers are the core foundation or building blocks for data/voice communication. There are unmanaged and managed switches. Unmanaged switches are plug in and go. They work right out of the box. They usually have less capacity than a managed switch and are most often found in home networks or desktop switches. Managed switches are more robust and have a much richer feature set allowing them to be configured, monitored locally or remotely, giving you much more flexibility and network control.