A disclaimer is a statement on the face of a registration that reads something like NO CLAIM IS MADE TO THE EXCLUSIVE RIGHT TO USE "BREWERY" APART FROM THE MARK AS SHOWN.  It basically means, as the text suggests, that you aren't claiming the exclusive right to a descriptive term, like BREWERY, BREWING CO., IPA, or STOUT.  Disclaimers are very typical but you should be careful when agreeing to enter them as they can limit the scope and strength of your registration.