The client is the initiating party that sends an API request. Often times there will be many clients consuming the same API.
A client is anything that can obtain a service provided by another server. Fat Clients are clients that performs the majority of the logic and data processing itself, while a Thin Client presents preprocessed data to the viewer.
There can be many clients consuming a single API.
![Client Diagram](http://i.imgur.com/EVuUjWW.png "Client Diagram)