Rich, Thin,Thick client

• fat (heavy, rich,thick) client 

A fat client (also called heavy, rich, or thick client) is a computer (client) in client–server architecture or networks that typically provides rich functionality independent of the central server. Originally known as just a "client" or "thick client"[1] the name is contrasted to thin client, which describes a computer heavily dependent on a server's applications.

http://en.wikipedia.org/wiki/Fat_client

• Rich Client

The Rich Client mixes the characteristics of classical web applications and RIAs.
The web application is client-centric (i.e. the user interface is loaded to client at the start of the application).
The view uses HTML widgets, thus no plugin is required.
Contrary to RIAs, the goal of a Rich Client is NOT to offer a modern looking user interface, but to improve the usability of an already widespread and accepted view

http://www.kai-waehner.de/blog/2010/12/30/categorization-of-web-frameworks-in-the-java-environment/

• What is a thin client?

A thin client is a lightweight interface to the application that does not have such operations like query databases, execute complex business rules, or connect to  legacy applications.

• Thick vs. Thin Client Applications

A thin client machine is going to communicate with a central processing server, meaning there is little hardware and software installed on the user's machine. At times, thin may be defined as simply not needing the software or operating system installed on the user machine. This allows all end users' systems to be centrally managed and software deployed on a central server location as opposed to installed on each individual system.
Thin clients are really best-suited to environments in which the same information is going to be accessed by the clients, making it a better solution for public environments. For this reason, thin clients are often deployed in hotels and airports, where installing software to all systems wouldn't make sense. It would be a massive headache for IT to both deploy and maintain.

When using thin clients, compared to a feature-rich desktop PCs today, they often tend to look a bit primitive and outdated. Since many thin clients run on very little hardware, it is impossible to incorporate rich graphical user interfaces. To use the client, an input device (keyboard) and viewing device (display) is usually the basic requirements. Some may not even require a mouse.

In contrast, a thick client will provide users with more features, graphics and choices making the applications more customizable. Unlike thin clients, thick clients do not rely on a central processing server because the processing is done locally on the user system, and the server is accessed primarily for storage purposes. For that reason, thick clients often are not well-suited for public environments. To maintain a thick client, IT needs to maintain all systems for software deployment and upgrades, rather than just maintaining the applications on the server.  Additionally, thick clients often require operating specific applications, again posing more work and limitations for deployment. The trade-off is a more robust and local computing environment.


http://www.webopedia.com/DidYouKnow/Hardware_Software/2006/thin_client_applications.as