There is no exact way of classifying motions. Generally, they may be grouped into those motions that are self-contained and require notice and those that are dependent on some other proceeding or motion and do not require any notice. The first group includes substantive motions. The second group includes subsidiary motions (or ancillary motions) and privileged motions.
Substantive motions are independent proposals that are complete by themselves and are not incidental to or dependent upon any proceeding before the House. They are used to elicit an opinion or action of the House. They are amendable and must be drafted in such a way as to enable the House to express agreement or disagreement with what is proposed. Such motions normally require written notice before they can be proposed in the House. They include, for example, private Members’ motions, opposition motions on supply days, and government motions.
Subsidiary motions, also known as ancillary motions, are procedural in nature, are dependent on an order already made by the House, and are used to move forward a question already before the House. For example, motions for the second and third readings of bills as well as motions to refer a matter to a committee are subsidiary motions, which are debatable and amendable. Like privileged motions, they may be moved without notice.
A privileged motion (not to be confused with a motion based on a question of privilege) differs from a substantive motion in that it arises from and is dependent on the subject under debate. A privileged motion may be moved without notice when a debatable motion is before the House; the privileged motion then takes precedence over the original motion under debate. Privileged motions can be either amendments or superseding motions, such as the previous question or dilatory motions. Both types seek to set aside the question under consideration and may be moved only when that question is under debate.