The Siddur is our traditional prayer book, containing the three daily prayers; also the prayers for Shabbat, Rosh-Chodesh and the festivals. "Siddur" means "order," for in the prayer book we find our prayers in their proper and fixed order. Sometimes, for the sake of convenience, the Shabbat and Rosh-Chodesh prayers may be printed in a separate volume. The prayers for Rosh Hashanah and Yom Kippur are usually printed in separate volumes, called machzor ("cycle"). Sometimes the prayers for the Three Festivals (Shalosh Regalim) — Passover, Shavuot and Sukkot — are also printed in separate volumes.
The oldest prayer book that has come down to us is the prayer book of Rav Amram Gaon, Head of the Yeshiva of Sura, in Babylon, about 1100 years ago. He had prepared it at the request of the Jews of Barcelona, Spain. It contains the arrangements of the prayers for the entire year, including also some laws concerning prayer and customs. It was copied and used not only by the Jews of Spain, but also by the Jews of France and Germany, and was in fact the standard prayer-book for all Jewish communities. Seder Rav Amram Gaon remained in handwritten form for about 1000 years, until it was printed for the first time in Warsaw in 1865.
Rav Saadia Gaon, who was head of the Sura Yeshiva less than 100 years after Rav Amram Gaon, arranged a prayer book for the Jews in Arab countries, with explanations and instructions in Arabic. The Rambam (Rabbi Mosheh ben Maimon, also known as Maimonides), in his famous Code of Jewish Law, also prepared the order of the prayers for the whole year (including the Haggadah of Passover), following the section dealing with the Laws of Prayer. One more of the old prayer books to be mentioned is the Machzor Vitri, composed by Rabbi Simcha Vitri, a disciple of the great Rashi, and completed in the year 1208.
Nusach means "text" or "form," and is sometimes referred to also as Minhag, which means "custom" or "rite." When we pick up a prayer book, there will be an indication on the front page what Nusach or Minhag the prayer book belongs to, such as Nusach Sfard (Spanish), Nusach Ashkenaz (German), Nusach Polin (Polish), Nusach Ari (arranged according to the saintly Rabbi Yitzchak Luria), etc.
It should be understood that in all these various prayer books the main body of the prayers is the same, but there are certain differences in the order of some prayers, minor changes also in the text of some, additions of piyyutim (poetical hymns composed by saintly authors).
According to the explanation of the Maggid of Mezeritch, there are as many as 13 Nuschaoth, forms, of prayer or Minhagim, customs of prayer. Each Nusach represents a tribe or "gate," and the Ari composed a "General Nusach-Gate" through which any Jew can enter into the presence of G‑d.
We have already mentioned that the Seder Rav Amram Gaon served as the standard prayer book for most Jewish communities dispersed throughout the world, inasmuch as it was based on the Talmud and Tradition. But in certain communities there were local Minhagim (customs), including certain piyyutim, which in time became standard for those communities. The main Nuschaoth were those of Sfard and Ashkenaz, as well as of the Italian Jews. The first printed prayer book was that of Minhag Romi (Roman, or Italian, Jews). It was printed in Soncino (Italy) in 1486. The first Nusach Ashkenaz prayer book was printed in Prague in 1513 (part 2 in 1516), and the first Nusach Sfard was printed in Venice in 1524. In due course many other prayer books were printed according to the customs of Polish, Rumanian, Balkan, and other countries where the Nusach differed. When the saintly Rabbi Yitzchak Luria arranged the prayer book according to the Kabbalah, many communities adopted it, and a new series of Nusach Ari prayer books were printed. Printers were not always careful in the printing, and errors were not uncommon. Finally, the great Rabbi Schneur Zalman of Liadi, who was both a great Talmudist and Kabbalist sifted some 60 different prayer books and arranged the Nusach in accordance with the original Nusach Ari which became known as Nusach Chabad.
But whatever traditional Nusach one follows, it is sacred and acceptable to G‑d. The important thing is to pray with devotion, with love, reverence, and mercy, as explained earlier.
Whatever Nusach is yours, you will find the structure of the prayers basically the same. The Morning prayers begin with the Morning Blessings, continue with Pesukei d'Zimra (Psalms and sections from the Torah, introduced by a benediction and concluded by a benediction), followed by the Shema (which is also introduced and concluded by a benediction), and then comes the main prayer, the Shemone Esrei ("Eighteen"—actually, nineteen benedictions), known also as the Amidah ("standing," because it must be recited in a standing position). Then follow a series of other prayers, concluding with Aleinu.
We have already mentioned that our Sages declared that the ladder which our Patriarch Jacob saw in his dream, and which "stood on the earth but reached into the heaven," was also symbolic of prayer. Indeed, our prayers are so arranged that they lead us step by step higher and closer to G‑d. This will become more evident as we get better acquainted with the plain and inner meaning of the blessings and prayers.