The word Maariv is the first significant word in the opening blessing of the evening service. It is derived from the Hebrew word erev, which translates to evening. Maariv is a conversion of this word into a verb, which means "bringing on night." "Arvit" is the adjective form of this word, roughly translated as "of the evening".
Maariv was not originally part of the daily prayers, which corresponded to the morning and afternoon tamid offerings. It then became a universal custom among the Jews to recite a prayer during the evening, linking it with both the continued burning of the sacrifices into the night as well as the evening recitation of the Shema.
Rabbinical tradition posits that Maariv was instituted by Jacob, based on Genesis 28:11. Wein posits that he first started reciting the prayer after he fled from his homeland, and as a result, the prayer service has become associated with trust in God.
Time frame for recitation 
Generally, the time when Maariv can first be recited is when the time for reciting Mincha ends. But there are varying opinions on this. Maariv should not begin before 1¼ hours before shkia (sunset). Others delay Maariv until after sunset or after dusk. This is so the Shema can be recited in its proper time. To satisfy this requirement, if Maariv is recited prior to this time, the Shema is repeated later in the evening.
Back-to-back Mincha and Maariv 
In many congregations, the afternoon and evening prayers are recited back-to-back, to save people having to attend synagogue twice. The Vilna Gaon discouraged this practice, and followers of his set of customs commonly wait until after nightfall to recite Ma'ariv (the name derives from the word "nightfall").
On Shabbat 
On the eve of Shabbat, some have the custom to recite the Maariv prayer earlier than usually, generally during Pelag Hamincha (1¼ hours before sunset). This is in order to fulfill the mitzvah of adding from the weekday to the holiness of Shabbat. However, this is too early for the recitation of Shema, so Shema should be repeated later under these circumstances.
Prayers included 
This service begins with the verses "But He is the merciful..." and "God, save!...". Then comes Barechu, the formal public call to prayer, and Shema Yisrael embraced by two benedictions before and two after. Ashkenazim outside of Israel (except Chabad-Lubavitch and followers of the Vilna Gaon) then add another blessing (Baruch Adonai L'Olam), which is made from a tapestry of biblical verses. (This prayer is also said by Baladi Temanim in and out of Israel, albeit combined with the last blessing.) This is followed by the Half Kaddish, and the Shemoneh Esreh (Amidah), bracketed with the full Kaddish. Sephardim (and, in Israel, most who follow Nusach Sefard) then say Psalm 121 (or another topical Psalm), say the Mourner's Kaddish and repeat Barechu, before concluding with the Aleinu. Ashkenazim, in the diaspora, neither say Psalm 121 nor repeat Barechu, but conclude with Aleinu followed by the Mourner's Kaddish (in Israel, Ashkenazim do repeat Barechu after mourner's Kaddish). The Maariv service consists of the following prayers:
- Barechu (with a minyan)
- HaMaariv Aravim
- Ahavat Olam
- Shema Yisrael
- Emet V'Emunah
- Baruch Adonai L'Olam (weekdays only)
- Veshamru (Shabbat only)
- Half Kaddish
- Vaychulu (Shabbat only)
- Seven-faceted blessing (Shabbat only)
- Full Kaddish
- Sefirat HaOmer (between Passover and Shavuot)
- Mourner's Kaddish
Unlike during Shacharit and Mincha, the Amidah is not repeated during Maariv. This is because of a Talmudic ruling that Maariv is considered optional. There were also no offerings in the temple at night, and the lack of a repetition serves as a reminder of this. Despite this ruling, observant Jews consider Maariv to be just as important as Shacharit and Mincha.
Maariv after Shabbat 
During the Maariv service following Shabbat, several additions are made.
A paragraph called "Ata Chonantanu" is inserted into the fourth blessing of the Amidah. The recitation of this paragraph officially ends Shabbat. One who forgets to recite this paragraph may also end Shabbat through Havdalah or by saying the words "Blessed is He Who differentiates between the holy and the secular." Two sections of prayers beginning with the verses "Vihi Noam" (the last verse from Psalm 90, followed by the full Psalm 91, and V'Ata Kadosh (all but the first two verses of Uva Letzion)) are added to the service. Nusach Ashkenaz also adds "Veyiten L'Cha" (whereas Sfardim and Nusach Sfard say this at home after Havdala). These prayers are recited out of mercy for the wicked. The wicked are given a reprieve from Gehinnom during Shabbat, and the reprieve continues until all evening prayers following Shabbat are concluded.
Other additions 
In general, relatively few prayers are added onto Maariv, even on holidays, although there are exceptions. On Simchat Torah, the Torah is read during Maariv. On Purim, the Book of Esther is read, followed by V'Ata Kadosh, and on Tish'a Ba'av the Book of Lamentations and some kinnot are recited, also followed by V'Ata Kadosh. On Yom Kippur, an extended order of Selichot is recited, followed by Avinu Malkeinu (except on the Sabbath). On both Rosh Hashanah and Yom Kippur, many congregations recite Psalm 24.
See also 
- Living Jewish: values, practices and traditions By Berel Wein, page 88
- Mishneh Torah, Hilkhot Tefillah 1:6
- Living Jewish: values, practices and traditions By Berel Wein, page 90
- To pray as a Jew: a guide to the prayer book and the synagogue service By Hayim Halevy Donin, pages 340-41
- In strict law, one should only recite Mincha between sunset and nightfall if one recites Arvit after nightfall; conversely one should only recite Arvit between sunset and nightfall if one recites Mincha before sunset; in other words one should not take advantage of both flexibilities at once so as to combine the prayers. The prevailing practice, of doing exactly that, is regarded as an emergency measure. On yet another view, the disputed period is not that between sunset and nightfall but the last seasonally adjusted hour and a quarter before sunset.
- One reason for this is that, while the prevailing practice may satisfy the law concerning the timing of Arvit in the sense of the evening Amidah, it means that the evening Shema is recited too early.
- Concise Code of Jewish Law By Gersion Appel, page 60
- To pray as a Jew: a guide to the prayer book and the synagogue service By Hayim Halevy Donin, page 72
- e Code of Jewish Law By Gersion Appel, page 409
- Concise Code of Jewish Law By Gersion Appel, page 410