A mosque is a place where followers of Islam (commonly known as Muslims) gather to practice their religion. Traditionally used as a place to perform the five daily ritual prayers, modern mosques are more elaborately constructed than they were in ancient times.

In addition to being a place to pray, mosques have become meeting places where Muslims do fellowship activities and study Islam.

While a mosque serves many of the same functions as Jewish temples and Christian churches, it should be noted that since Muslims believe they have a direct connection with God, they have no clergy in the sense that Jews and Christians think of the term.

Although the term mosque is used in English to refer to a mosque of any size, Muslims differentiate large community mosques and smaller, private mosques with slightly different nomenclature.

From Wikipedia.com

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The word mosque in English refers to all types of buildings dedicated to Islamic worship, although there is a distinction in Arabic between the smaller, privately owned mosque and the larger, "collective" mosque
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A mosque is a place where Islamic believers can come to worship Allah and pray. In early days, mosques were always a city centres or a city district center and were surrounded by a circle of shops, hospitals or courts. A believer enters a mosque having taken the shoes off as a respect to the holy place. In certain Muslim countries women are not allowed to enter a mosque. They stay home and pray when their husbands go to the mosque. A mosque does not have pews as a church, believers usually bring a small mat for kneeling that they spread out on the floor before the beginning of prayer. Prayer time is five times a day, and a noon prayer on Friday is the most important. Hundreds of people gather in mosque on Friday to offer Allah their prayers.