There can be up to 3 motions on the floor at the same time. The Mayor/Chair can reject a 4th motion until the body has dealt with the 3 on the floor. This rule has practical value; more than 3 motions on the floor is confusing and unwieldy.
When there are 2 or 3 motions on the floor (after motions and seconds) at the same time, the vote proceeds first on the last motion that is made. For example, assume the first motion is a basic motion to have a five-member committee to plan the annual fundraiser. "During the discussion of this motion, a member might make a second motion to "amend the main motion to have a ten-member committee, not a five-member committee, to plan the annual fundraiser. And perhaps, during that discussion, a member makes yet a third motion as a "substitute motion that we not have an annual fundraiser this year." The proper procedure would proceed as follows:
First, the Mayor/Chair would deal with the third (the last) motion, the substitute motion. After discussion and debate, a vote would be taken first on the third motion. If the substitute motion passed, it would be a substitute for the basic motion and would eliminate it. The first motion would be moot, as would the second motion, and the action on the agenda item would be completed on the passage of the third motion (the substitute motion). No vote would be taken on the first or second motions.
Second, if the substitute motion failed, the Mayor/Chair would then deal with the second (now the last) motion, the motion to amend. The discussion and debate would focus strictly on the amendment (should the committee be 5 or 10 members). If the motion to amend passed, the Mayor/Chair then proceeds to consider the main motion (the first motion) as amended. If the motion to amend fails, the Mayor/Chair would then proceed to consider the main motion (the first motion) in its original format, not amended.
Third, the Mayor/Chair would now deal with the first motion. The original motion would either be in its original format (five-member committee), or if amended, would be in its amended format (10-member committee). The question on the floor for discussion and decision would be whether a committee should plan and put on the annual fundraiser.