"The fundamental rule of the House of Representatives governing debate is the one-hour rule. Clause 2 of Rule XVII states in part that no one shall 'occupy more than one hour in debate on a question in the House.' When the House debates a bill on the floor under this rule, the bill is said to be considered 'in the House.' The House considers bills on the floor under the one-hour rule unless it resorts to one of the alternative packages of floor procedures provided under House rules, especially the Committee of the Whole and motions to suspend the rules. In some cases, a primary advantage for choosing one of these alternative procedures is that they avoid some of the difficulties that can arise when the House debates a bill under the one-hour rule. In theory, the one-hour rule allows each Member of the House to speak for an hour on any question, meaning not only each bill but also each amendment to that bill and each debatable motion that Members propose during the bill's consideration. Potentially, the result could be debates of interminable length, which could make it impossible for the House to complete its legislative work in a timely fashion. In practice, however, the one-hour rule typically limits all Members of the House to a total of only a single hour of debate on the bill and any amendments and motions relating to its passage. This can be insufficient time for the House to consider many of the important and controversial bills that it takes up each year. As a result, the House actually debates relatively few bills on the floor each year under the one-hour rule."
CRS Report for Congress, 98-427
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html