(from the web2py manual)
4.14 init Application
When you deploy web2py you will want to set a default application i.e. the application that starts when there is an empty path in the URL, as in:
By default, when confronted with an empty path, web2py looks for an application called <b>init</b>. If there is no init application it looks for an application called <b>welcome</b>.
Here are three ways to set the default application: • Call your default application "init". • Make a symbolic link from "applications/init" to your application’s folder. • Use URL rewrite as discussed in the next section.
(see 4.14 URL Rewrite)