From local forum i understood that PreInit can be used to handle the following

PreInit()
>Master pages can be called dynamically
>Themes can be set dynamically
>Programatically add controls to controls collection

and i read Init() is for

Init()

In this event, we can read the controls properties (set at design time). We cannot read control values changed by the user because that changed value will get loaded after LoadPostData() event fires.

Question

I am not getting the point "We cannot read control values changed by the user".Where do users change the value of control?.Example would help me to understand the point.