What's isset($_GET['ajax'] for in the generated code?

Yii 1.1 General Discussion
1

In the actionDelete() of the generated code, there is


if ( ! isset($_GET['ajax']))

. What’s this for? I’ve never seen &ajax=… in URLs.

2

When using CGridView with a CButtonColumn, there is a delete button, which makes an ajax call, and sends that paramenter to be identified.