It means that the stuff in quotes, apart from the mark as a whole, cannot be claimed by them as a trademark.
When you see it as the claimed mark in a UDRP case, it means you have major morons on your hands:
http://www.cpradr.org/ICANN/icanndecisioncpr0601-060302.pdf
In viewing the effect of disclaimers, the US Circuit Court of Appeals for the Eleventh Circuit in Lone Star Steakhouse & Saloon, Inc. v. Longhorn Steaks, Inc., 41 U.S.P.Q.2d 1896 (CA11 1997) stated at page 1902, quoting from McCarthy on Trademarks and Unfair Competition (3d ed. 1992) at § 19.20 [1]:
'The disclaimer does not have the effect of removing from the registered mark the matter disclaimed. It disclaims only a claim that the federal registration gives an exclusive right in those disclaimed words or symbols per se. That is, the applicant is merely stating that he is claiming only the whole composite mark as his property, and makes no claim to those particular portions disclaimed'. "
You can probably learn a lot more about why & when the disclaimer was required by reading the file history of the registration in question, which you can access from the USPTO site under the "documents" link from the trademark section.
Typically, the disclaimer is required for a generic word within a compound mark relating to that class of goods.