The previous question is a motion, “That this question be now put”. It has two functions:
The previous question may be moved only by a Member who has been recognized to speak during the regular course of debate. It cannot be proposed while an amendment to the main question is being considered. While the previous question is debatable, it is not amendable. The previous question cannot be moved in a Committee of the Whole or in any committee of the House.
The previous question does nothing to hinder debate on the original motion. What is relevant to the previous question is also relevant to the original motion. Nonetheless, after the previous question has been moved, Members are eligible to participate in debate even if they have already spoken to the main motion.
When debate on the motion for the previous question has concluded, the question is put to the House. If the previous question is resolved in the affirmative, the Chair immediately, without further debate or amendment, puts the question on the original motion. If the motion to move to the previous question is defeated, resolving that the question be not now put, the Speaker is bound not to put the main question at that time. The main motion is superseded, the House proceeds to its next item of business, and the main motion is removed from the Order Paper.