Black's Law Dictionary (9th edition) defines a "motion" as: "A written or oral application requestiong a court to make a specified ruling or order."
That is, if you are involved in a court case and you want to get something done, you need to file a motion with the court. There are many kinds of motions.
Rules 9A through 9E of the Massachusetts Superior Court Rules govern how, when, and in what form motions must be made in civil cases in the Superior Court. As of January 1, 2014, Rule 9A will have an additional sentence, in section 9A(b)(2), which will clarify the time period required to respond to a motion by an opposing party, if one wants to oppose that party's motion.
The additional sentence reads as follows: "If the motion is served by mail, these time periods shall be increased by 3 days pursuant to Mass. R. Civ. P. 6(d)."
You can read the entire Rule 9A, and Massachusetts Rule of Civil Procedure 6, to which it refers, as well as all the court rules for all the different courts on the Massachusetts Rules of Court webpage of the Massachusetts Trial Court Law Libraries.