The third of the daily prayers, called Maariv, or Arvit, is recited at nightfall (the first two are recited in the morning and evening). This prayer was instituted by Patriarch Jacob.
In fact, considering that the Jewish day begins at night, Maariv is the first prayer of the day. The words of the prayer engage the body in the service of God, elevating and refining it so that it is more attuned to the spirit. In the initial process of refinement, the body is in a state of spiritual darkness; therefore, Maariv is the first prayer of the day.
From nightfall (tzet hakochavim, the three middle stars in the night sky) until dawn, one may recite the Maariv prayer. (It is also permissible to pray Maariv early, up to 1¼ halakhic hours before sunset, provided that the afternoon (Mincha) prayer has been recited before this time. This time is called Plag Hamincha. If one prays Maariv at this time, the Shema must be recited again at nightfall.).
Maariv begins with the recitation of the blessings preceding the Shema, followed by the Amidah (nineteen blessings recited standing) facing Jerusalem. It concludes with the Aleinu, taking approximately ten minutes in total. On Shabbat or holidays, it varies according to the day.