A Mosque is a building dedicated to worship in Islam. A mosque is a place of worship for followers of Islam. Muslims often refer to the mosque by its Arabic name, masjid.
All adult Muslims, with exceptions for the infirm, are required to offer Salat (prayers) (sometimes called Namaz) five times daily. Most mosques will organise a formal time of prayer for each of the daily timeslots. In addition to holding the daily prayers, mosques hold weekly jumu'ah services which replace the midday prayer on Fridays. While daily prayers can be performed anywhere, it is required to attend Friday prayers at the mosque.
Muslims at prayer (salat) in a Mosque
A Church building is a building or structure whose primary purpose is to facilitate the meeting of a church. (Church iteself means "gathering or assembly of people for worship). So Christian Churches are places where Christians gather for worship.
A Christian Church
Originally, Jewish Christians met in synagogues, such as the Cenacle, and in one another's homes. As Christianity grew and became more accepted by governments, rooms, and eventually entire buildings, were set aside for the explicit purpose of Christian worship.
Christian worship usually happens on a Sunday, although many Churches are used for prayer and worship during the week. Some Christian faiths have worship services every day in the Church.