This brief article from Chabad.org describes the structure of the Kabbalat Shabbat and Ma'ariv even prayer services on Shabbat. With a focus on prayer as the essence of Shabbat, the author describes how regular weekday prayer are adapted to reflect the special spirit of this day.
Greeting the Shabbat
Six days a week we work, eat, sleep, exercise…and we also pray. Then, on the seventh, we pause to reconnect with the Creator. Now prayer is not just another item on the task list; it’s part of the day’s definition. Without the pressures and distractions of the workweek, we become more contemplative and focused—just the state required for real prayer.
As evening descends, we greet the holy day with Kabbalat Shabbat (“Welcoming the Shabbat”). In most congregations, this service starts with six psalms (representing the six days of the week), followed by a deeply mystical song to joyously welcome the Shabbat Queen, Lechah Dodi. This is followed by another two psalms that relate to Shabbat. Next comes either a selection from the Zohar that discusses the mystical dynamics of Shabbat’s entry, or the recitation of a chapter of the Mishnah comprising some basic Shabbat laws—depending on custom.
Kabbalat Shabbat is followed by the standard evening service, adapted to the spirit of the day, including the Shabbat Amidah. After this, the congregation chants the biblical verses about G‑d creating the world in six days and resting on Shabbat. This is followed by a brief Shabbat prayer, one more psalm, and the service concludes with the Aleinu hymn.
Something you will likely notice: The weekday Amidah comprises nineteen blessings; the Shabbat Amidah, only seven. The thirteen middle blessings beseeching G‑d for our needs would jar with the tranquility of Shabbat, so we replace them with one blessing proclaiming the holiness of the Shabbat and thanking G‑d for this precious gift.