"Privileged business relates to the order or priority of business before the House and is defined in House rules and precedents as business that has precedence over the regular order of business. As a consequence, it may supersede or interrupt other matters that might be called up or pending before the House. Members have a right to call up privileged business for consideration on the floor when the House is not engaged in considering some other matters. Privileged business consists of various kinds of bills, resolutions, and other matters. Clause 1 of House Rule XIV defines the daily order of business on the House floor. However, other House rules and precedents allow certain kinds of matters to interrupt this daily order of business. A matter that can interrupt the daily order of business is said to be privileged. In practice, the House never follows the daily order of business that Rule XIV defines. Instead, virtually all the legislative business that the House transacts on the floor each day--after the opening prayer, the approval of the Journal, and the Pledge of Allegiance--is conducted either by unanimous consent or as a privileged interruption of the daily order of business."
CRS Report for Congress, 98-315
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html