The adhan (also spelled Athan, Azan, Ezan) is the Islamic call to prayer. The Muslim call to Friday public worship and to the five daily hours of prayer. It is proclaimed by the muezzin, a servant of the mosque chosen for good character, as he stands at the door or side of a small mosque or in the minaret of a large one. The adhan was originally a simple "Come to prayer," but,
according to tradition, Muhammad consulted his followers with a view to investing the call with greater dignity. The matter was settled when 'Abd Allah ibn Zayd dreamed that the faithful should be summoned by a crier. The standard Sunnite adhan can be translated as: "Allah is most great. I testify that
there is no god but Allah. I testify that Muhammad is the prophet of Allah. Come to prayer. Come to salvation. Allah is most great.
There is no god but Allah." The first phrase is proclaimed four times, the final phrase once, and the others twice, the worshipers making a set response to each phrase.
It’s simply a way to alert people when they are busy; that the time for the prayer (“Salah” in Arabic; one of the 5 pillars of Islam) has come. Especially in the Muslim world; because in Islam, the five daily prayers are supposed to be carried out in congregation as much as one can. And so in
the old days, before the development of
technologies (alarm clocks,
mobile phones, etc) that was a fast way to let people know. Recently, in the past fifty years or so, they started using loudspeakers on top of minarets to call the adhan. It’s a beautiful and enchanting sound and it’s just calling people to come and worship.