Shopping Cart Control - Update Statement

I have a control named as ShoppingCartControl. In it, there is an update button. The code behind that is :-

protected void ctrlShoppingCart_ItemUpdating(object sender, ItemEventArgs e)
        {
            ShoppingCartControl control = sender as ShoppingCartControl;
             int qty=0;
            
            foreach (var c in control.Items)
            {
                int recid = ((ShoppingCartControlItem)c).ShoppingCartRecId;
                if (recid == e.ID && e.ID!=null)
                {
                    qty = ((ShoppingCartControlItem)c).Quantity;
                }

            }
            cart.SetItemQuantity(e.ID, qty);
            Response.Redirect("shoppingcart.aspx");
        }

Can anyone explain me this code step by step or what is meant by "sender as ShoppingCartControl".



Thanks and Regards
Akiii