Inside the config folder you will find several .ini and .xml files
In order to keep your config files clear and easy to read you should use multiple files. each file found in the application/config/ folder is loaded, so you can split your configuration.
By default there is
an application.ini file (application/configs/application.ini)
for all general configuration of the application
a permissions.xml file (application/modules/Administrator/config OR application/modules/Members/config)
An XML configuration that indicates User or Admin access privileges and roles to control access to schema objects and to control the ability to execute system operations
a config.ini file (application/configs/config.ini)
the place to set the system default config including database configuration
host address, db credentials...
a layout.ini file
customizing default values of the layout goes here
a modules.ini file
the place to define which modules should be loaded in your application
a routes.ini file
for url rewriting rules define your application's route (as zend framework define route)
a lang.en_US.ini file (application/languages or application/modules/<$ModuleName>/languages )
place here the translation specific configuration
a form.ini file (application/modules\<$ModuleForm>/forms/source)
use this file as Form's pattern if you need to create new web form asking visitors to fill up.
Each configuration file, is divided into environments "development", "production", "staging", etc... that allows you to customize configuration for each step of your project's life cycle. for more information about ini file syntax see the Zend Framework documentation