object = object = object ? what is this code doing

Hi,
Can anyone explain to me what does this code means?

protected void Application_Start(object sender, EventArgs e)
{
    HttpContext.Current.Application["DS"] =
     HttpContext.Current.Cache["DS"] =   new BL.DS(conString).DS;
}


I am not sure if I am getting this .

 new BL.DS(conString).DS; // I guess creating a Dataset then
put it in a cach, then put the cach in application....
 am I right. Why would I do that anyway.

please explain

Thanks

Bob