The Front Controller

From here, the responsibility transfers to the front controller. The front controller has an array of “routers” that it uses to decide which module the URL should trigger. This correlation between URL and module name is defined in the config.xml files. The available routers are:
• Standard
• Admin
• Default (only used for 404s)
The definition of a match between a router and amodule looks like this for the Customer module:

<routers>
<customer>
<use>standard</use>

<args>
<module>Mage_Customer</module>
<frontName>customer</frontName>
</args>
</customer>
</routers>