Distinguishing between nginx and thin

A typical small application deployment will have Nginx(or Apache) and a handful of Thin(or Mongrel, Unicorn, etc) servers running all on one machine.

Nginx receives every request. It then serves and static files directly (css, js, images, cached stuff). If the request requires processing it then hands the request off to a rails process (Thin).

This way your (relatively) slow application servers are freed up from serving static files, and your web server is providing a sort of load balancing.

The benefit of Nginx/Thin over something like Apache/Mongrel is that Nginx/Thin can communicate directly via a unix socket, removing the overhead of communicating via the tcp/ip stack.

Thin is an application server while Nginx is a web server.

From http://www.javaworld.com/javaqa/2002-08/01-qa-0823-appvswebserver.html

The application server exposes business logic to client applications through various protocols, possibly including HTTP. While a Web server mainly deals with sending HTML for display in a Web browser, an application server provides access to business logic for use by client application programs. The application program can use this logic just as it would call a method on an object (or a function in the procedural world).

Speaking out of ignorance (I've never used Thin), it is quite normal to mix nginx and an application server together, using nginx to serve up static content and act as a reverse proxy for the application server.

This makes it easy to blend ludicrously fast static content serving with the application server of choice (which varies between programming languages), all coming from the same address:port.