Using a standard list controller is very similar to using a standard controller. First you set the standardController attribute on the <apex:page> component, then you set the recordSetVar attribute on the same component.
<apex:page standardController="Account" recordSetVar="accounts">
When you use the standardController attribute on the <apex:page> tag, you cannot use the controller attribute at the same time.
The recordSetVar attribute not only indicates that the page uses a list controller, it can indicates the variable name of the record collection. This variable can be used to access data in the record collection.