Common Network Components

Client:

It may be a desktop, laptop or smartphone or tablet but a client is how the user interfaces with a network.

File Server:

A file server can be thought as a computer which shares its hard drive with clients. File server is going to make files available to clients.

Switch:

It is referred to as a layer 2 device. It can make forwarding decisions based on what it learnt. It's decision is based on MAC(media access control) address. 

Router: 

It is a layer 3 device. It's gonna make forwarding decisions based on logical addresses.