A meeting place of worship or prayer house for Muslim
s. It's pronounced "Mosk." Most Muslims will refer to one with its Arabic
. This translates to "the place of prostration
" or "place of worship." It's a place formally dedicated to the saying of prayers. Although the prophet Muhammad
, peace be upon him, said that "the whole earth is a mosque," it is preferable to pray with others, hence the building.
Mosques play a vital role in the lives of Muslims. The primary function of the mosque is to provide a place where Muslims may perform their obligatory five daily prayers as a congregation. One can do it alone, but there's a greater blessing if it is done with others. The Prophet once said that it is an extra good deed to pray in a mosque, the reward for doing so is 27 times more than if made anywhere else. Prayer must be performed together on Friday afternoons, the Muslim day of communal prayer, and is strongly recommended on the two Muslim holidays, called Eids, or festivals.
Aside from prayer, mosques serve a variety of functions. It's often a place for meeting and social gathering, where one can reach out and connect with the local community. Most are open 24-hours, and you may usually find people inside learning or reciting the Quran. There are Islamic Sunday Schools, day care, Arabic classes, youth activities, Marriages, funerals, and potluck dinners. Many mosques serve as recreational centers, and can have libraries, classrooms, and offices. Mosques also unify the people; Rich and poor alike use the same mosque and pray side by side, in the same language.
You'll find it different than a Christian Church or Jewish Temple. A mosque has no altar or pews. It is a place that is specifically dedicated as a place of prayer. However, there is nothing sacred about the building or the place itself. Since one can pray anywhere (provided it's clean), the whole earth could be a mosque, which is why Muslims often pray at home, at work, or in public places. Many colleges have a Muslim organization on campus, groups reserve a room for prayer and call it a mosque. Mosques can vary in size from small chapels to large Islamic centers that hold thousands of worshippers. Mosques are known for their fabulous architecture, some of which date back to the 7th century, older that most Cathedrals. A large dome is common design, though not in all of them. Although the common perception among non-Muslims is that a mosque is a large and domed, Taj Mahal-esque building with spires, often in America it is a converted building, a home, office, or even old church or in one case, a bowling alley.
Many Mosques, especially larger or older ones, have a minaret, or a tower where the call to prayer is delivered. This is done 5 times a day, and is in Arabic. Nowadays, most have installed loudspeakers, and the muezzin does it from a microphone. In predominantly Muslim countries like Pakistan, the whole town can hear the call to prayer, and stores close for the few minutes of prayer, longer on Fridays.
A mosque has no pictures of anyone, no statues either, as they are forbidden (they could encourage idolatry). Instead, you may find ornate walls, nice designs. Frequently you may see a section of the Quran in Arabic written in calligraphy on a wall, or in a picture frame, recounting some important verse. Some give a commandment, others comment and praise the wonders of God. There are 99 names for Allah (Gracious, Merciful, etc) that are mentioned in the Quran, and they are listed on the walls. Arabic calligraphy of Quranic verses and names of Allah is a common and permissible way of decorating a mosque.
There is a great prayer hall called a musalla, which is oriented facing the Holy city of Mecca. In North America, this would be generally east. Prayer halls are open and uncluttered to accommodate lines of worshippers who stand and bow in unison. There are no pews or chairs, since prayer consists of bowing and prostrating oneself. Members of the congregation sit on the floor, which is commonly covered with large rugs or carpets. Muslims all stand in this hall facing the same direction, forming rows side by side, shoulder to shoulder.
Muslim men and women form separate rows when praying. The idea is that many people become distracted by looking at the attractive opposite sex instead of focusing on prayer. Some mosques offer a balcony for women. If there's one room, a curtain is placed as a partition from front to back, or the women stand in a row behind men, though there is no difference in God's eyes who prays in front of who.
Almost all mosques have some sort of mihrab, or niche in the wall that shows which wall faces Mecca. It's often decorated with Arabic calligraphy, and may have a curved shape. In addition, there is also a small pulpit to the right of the niche, known as a minbar. During the Friday prayer service, the imam (prayer leader) delivers a sermon from the steps of the minbar.
A person chosen as the imam leads the group in prayer. It's usually a man, unless the congregation is all-women. He stands in front, with all the rows behind him, facing the mihrab, which helps reflect his voice toward the congregation. Everyone prays together, the imam leading and everyone following his example, and all bow, straighten up, drop to their knees, then pray prostrate (face to the ground).
Prayer is usually short, and the prayer is repeated at different times throughout the day. The Mosque isn't needed for prayer, one can pray at work or at home, but it's encouraged to be done in groups, thus the purpose of the mosque. It's strongly reccomended to gather for prayer on Friday afternoon (salat-ul-Jummuh), Islam's equivalent to the sabbath, like the Christians and Sunday or the Jews and Saturday.
A person has to be in a state of Ablution(purity) before praying, so there is usually a washroom inside. Muslims are to wash their hands, faces and feet before they stand before God. Some of the large mosques in the East have a large fountain or well in a courtyard outside for this purpose, though you'll typically find two large bathrooms (male and female) with several faucets each.
When a Muslim enters, it is considered a Sunnah to perform two rakats (sets) of prayer. This is known as Tahiyyat al-masjid, giving salutations to the mosque. It was strongly recommended by the Prophet Muhammad, peace be upon him.
When a person is in a mosque, he or she must remember that it is a house of God, and must be given its due respect. Therefore, Muslims are encouraged to sit quietly and keep him or her self busy in prayer, dhikr and recitation of the Qur'an. A Muslim is asked not to raise their voice or engage in idle talk or argue with others. According to a hadith, one who sits in the mosque waiting for the next prayer to begin is (receiving rewards) as if he is performing the prayer.
Bookshelves are a common thing in mosques. You can find works of Islamic philosophy, theology and law, as well as collections of the traditions and sayings of the Prophet Muhammad. Copies of the Quran, Islam's revealed text, are always available to worshippers, and many mosques will allow you to take a copy home.
During the month of Ramadan, people congregate there before and after dawn, recite text from the Quran and draw strength from each other as they fast from sunrise to sunset. After sunset there is usually a feast of fast-breaking where Muslims congratulate each other on their progress.
Muslims are known for their hospitality. You can visit one, and anyone there will be happy to talk to you, answer any questions you have. I'd encourage every person to visit one once, see what effect it may have on you. Nobody makes you participate, you can go watch. In case you're worried, there are commandments in Islam that make it clear nobody is to pressure you to convert, so I felt quite comfortable visiting and chatting with some local Muslims.
Most, but not all mosques are open to non-Muslims. Many restrict entry to "the faithful" or just keep the prayer hall closed, or restrict it only during friday prayer. This happens most frequently in areas like Israel and Palestine since the community is worried about security, though some large prominent ones are open for tourists. The vast majority of "regular" mosques don't have these restrictions, and welcome visitors.
The most holy mosque on Earth is the Masjid al-haraam(The Sacred Mosque), in the holy city of Mecca, surrounding the Kaaba. The entire city is closed to non-Muslims, and every year millions of Muslims make a pilgrimmage to this place, fulfilling one of their pillars known as the Hajj. All 1.3 Billion Muslims around the world face the Kaaba in the center of the mosque when praying. When inside the mosque, instead of praying in straight lines, the people form circles around the Kaaba and pray, men side by side with women, all nationalities together in harmony.
The second most sacred and famous mosque is Masjid an-Nabawi(Mosque of the Prophet) in Medina, Saudi Arabia.
Masjid Al-Aqsa, "the Distant Mosque", is located in Jerusalem. It is the mosque that the Muslims originally prayed to, until Muhammad (pbuh) decreed that everyone face the Kaaba. This is the third most sacred mosque.
Some important Mosques include: Al-Quba Masjid, Umayyad Masjid in Damascus. Large cities have larger mosques.
Some photos of famous mosques can be found at http://www.islamicity.com/Culture/MOSQUES/default.htm
Thanks to heyoka and gritchka for the suggestions.