A point of order is a matter raised during consideration of a motion concerning the rules of parliamentary procedure.
Explanation and uses
A point of order may be raised if the rules appear to have been broken. This may interrupt a speaker during debate, or anything else if the breach of the rules warrants it. The point is resolved before business continues.
The point of order calls upon the chair to make a ruling. The motion is sometimes erroneously used to ask a question of information or a question of parliamentary procedure. The chair may rule on the point of order or submit it to the judgment of the assembly. If the chair accepts the point of order, it is said to be sustained or ruled well-taken. If not, it is said to be overruled or ruled not well-taken.
In organizations other than legislative bodies, the ruling of the chair may be appealed to the assembly in most cases. Unless the chair's ruling is overturned by tie or majority vote in the negative, it stands. (The vote that is taken is a vote on whether or not to uphold the decision of the chair, so if the motion fails the decision is overturned.)
Until recently in the British House of Commons it was required that a member raising a point of order while the House is voting by wearing a hat so they could be easily seen, and two hats were kept in the House for such occasions. This practice has now been abolished. 
In the United States Senate, the chair's ruling may be appealed by any Senator. The Senate votes on the appeal and the chair has been frequently overturned. Points of order with regard to the Budget Act or annual budget resolution may be waived by 3/5 of the Senate's entire membership. Rule XVI, which prohibits normal legislation in appropriations legislation, may be waived by 2/3 of the Senate. 
In the United States House of Representatives tradition, appeals are also possible, but rarely entered and almost never succeed.
In the Irish Oireachtas (parliament) a point of order is "a submission to the chair in respect of a decision he has not yet taken with a view to influencing that decision by presenting certain facts or arguments." This cannot arise in relation to a decision already taken and must relate to a procedural item in the House or on the Standing Orders. A point of information cannot be raised when the Chair (Ceann Comhairle or Cathaoirleach) is: 1) dealing with disorder, 2) putting a question, 3) addressing the House or 4) dealing with an order of the house. These rules come mainly from precedent and common practice, as there is no provision in the official Standing Orders  for Points of Order. They are, however, usually dealt with in the standing orders as motions.
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