At first there was no fixed liturgy, for the prayers were not set down in writing; only the gist of their content was fixed, while the precentor provided their formulation. Public prayer was brief, and when it came to an end, the individual worshiper laid out an individual petition in silence. . . . The ancient prayers could not be lengthy, and their content had to be clear and simple; there was no room for convoluted language or structure. But once these prayers had become entrenched, they were subject to continual unconscious expansion, resulting from the need for innovation, changes in taste, outside influences, and the practice of individual spiritual leaders. These expansions consisted of wordier development of existing themes, the insertion of biblical verses and verse-fragments into the text, and poetic embellishment of the established text.
Even though the liturgy has become increasingly fixed, personal prayer remains essential. Time is specifically set-aside for private prayer at the conclusion of the Amida, the central prayer of every service. Personal prayer is by no means limited to this one part of the service, or even to services at all; we are encouraged to pray whenever and wherever we wish. In recent times, many Jews have composed alternate forms of prayer that they find more compelling than the traditional formulas. Other Jews find strength in retaining the prayers that have been uttered for generations.
There are three prayer services a day:
Shacharit--morning prayers, the longest of the three services
On Shabbat and holidays, Orthodox and Conservative Jews add a fourth service, Musaf, which comes immediately after Shacharit and replaces the special Shabbat/holiday offering given in the Temple.
All services center around the Amida or Shâmona Esrei, which consists of nineteen blessings praying for everything from health to forgiveness to return to Israel.
Jewish prayer is meant to be communal as well as individual. In order to recite all of the prayers of a service, ten people (in Reform, Reconstructionist and Conservative services) or ten men (in Orthodox and some Conservative services) must be present. (this is called a minyan) Within this communal prayer, there is always time for individual reflection.
Jews are also encouraged to pray individually and to pray at times other than those set by tradition.