Just like a Siddur is used for Tefilah (prayer) on a daily basis and on Shabbat, a machzor is used over Rosh Hashanah. The word “machzor” literally translates to the world “cycle” because each time we use the Rosh Hashanah machzor, it means we have come full cycle. The prayers on Rosh Hashanah are very different from the regular Tefilah and those said on Shabbat, and are also much longer, meaning an entirely different book is needed. There are different machzors for the High Holidays (Rosh Hashanah and Yom Kippur), as well as for the three pilgrimage holidays of Sukkot, Passover, and Shavuot.