Stacking

I have finally learned a new trick to this stacking thing!  Darius and Alicia thanks for trying to explain but it never clicked! For those of you whom was just as slow as I am stacking is when you have a manufactured coupon AND a store coupon for the same product some stores allow you to use BOTH.  For example, say Airwick sent me a coupon and then I go to my mailbox and dollar general send me a coupon for THEIR airwick product.  I can use BOTH!!!! Does this make sense?