Firstly, the Jewish establishment for prayer and worship is called "synagogue", "temple", or by Ashkenazi (East-European) Jews, "shul". The Hebrew term "beit-knesset" literally means "house of assembly". The community that uses a particular synagogue is usually led by a rabbi who tends to its spiritual, and mainly Halachic, problems (Halacha: the Jewish law, as determined by rabbis throughout the ages); the presence of a rabbi also encourages the existence of organised lessons within the synagogue. The prayer itself, however, is headed by a person whose sole responsibility is to pray over the voices of the congregation and read out key phrases, thus keeping the prayer in unison - a title called "chazan". Finally, the "gabai" is someone who oversees the synagogue's activity by assigning individuals with Torah readings (a portion of the Torah is read twice a week, plus on Shabbat and holidays); it's also a role that occasionally comprises the management of donations given to the synagogue. Most synagogues do not represent any religious group (as Judaism as a whole is largely non-denominational), and their only authority is the community itself. A conventional synagogue holds three prayers a day (assuming that there's a minyan - 10 people, the minimum number for group prayer) - morning, afternoon, and evening - not including special prayers for Shabbat and holidays. Prayers are read from the siddur - a uniform book of prayers for each occasion, with only minor variances between European and Eastern communities.