Final answer:
A motion to limit or extend limits of debate when no business is pending is categorized as an incidental motion in the context of legislative procedure. It is a key feature of the deliberative nature of the United States Senate, which traditionally allows for unlimited debate unless controlled by specific motions such as cloture or tabling.
Step-by-step explanation:
If a motion to limit or extend limits of debate is made when no business is pending, the class of motions it belongs to is incidental motions. Incidental motions are procedural motions that relate directly to another motion or to the business at hand, and must be decided immediately before the business can proceed. In the context of the United States Senate, there is a tradition of unlimited debate, which allows for extensive discussion on legislation until a motion to table is offered or until 60 senators vote in favor of a cloture motion to end the debate, overcoming a filibuster.
It is important to note that unlimited debate and the ability to extend or limit debate are significant components of the legislative process in the Senate. They are part of a broader set of rules and traditions designed to protect minority interests and ensure that legislation is thoroughly considered. The imposition of debate limits, if agreed upon by the body, is an example of how the Senate can manage its workflow while maintaining the tradition of being a deliberative body.