Web service lets you run web apps and web application frameworks such as Ruby on Rails.
OS X Yosemite doesn’t have specific support for Ruby on Rails, but you can download and install Ruby on Rails or other HTTP server frameworks to make your apps available by configuring reverse proxies in Apache with the webapp.plist(8) mechanism.
In addition to using the Server app, you can start or stop web service and inspect web service settings by using the servermgr_web and webappctl commands. For information about these commands, enter man servermgr_web and man webappctl in Terminal.
You can define the web apps managed by webappctl by creating plist files and placing them in /Library/Server/Web/Config/apache2/webapps/. For information about these plist files, enter man webapp.plist in Terminal.