DELETE And UPDATE Trigger Question

Hello
I have a Trigger on a table. Here is the code
 ALTER TRIGGER [dbo].[OnOrderDelete]
ON [dbo].[orders]
AFTER DELETE,UPDATE
AS
BEGIN
SET NOCOUNT ON;
DECLARE @ids int;
SELECT @ids =( SELECT id from DELETED);
DELETE FROM files WHERE OrderId = @ids;
END
Actually the UPDATE event handler is not wanted here, but why when I leave him I have a following behaviour:
When orders table is updated, the "SELECT @ids =( SELECT id from DELETED);
DELETE FROM files WHERE OrderId = @ids;" 
part is executed, and the program recognizes DELETED as UPDATED! (Like " SELECT @ids =( SELECT id from UPDATED) ")
Is this right? And how can I part UPDATED and DELETED ?

Thanks
Artashes