A minaret is a tall, slender tower which is attached to a mosque, a Muslim place of worship. There are a number of uses for minarets, but perhaps the most famous is the traditional call to prayer, which is often issued from the balconies minarets. Many people associate minarets with Muslim culture and the Muslim world, and they are common features in the cityscapes of Muslim regions, where the horizon may be dotted with an assortment of minarets of all shapes and sizes.
Muslims actually consider minarets to be bid'a, or “innovations.” The first minaret was built long after the Prophet Mohammad died, and therefore minarets are not part of the traditional practice of Islam. Minarets also do not appear to have been built specifically for the purpose of issuing the call to prayer or adhan, which was initially issued from the roof of the mosque or called in the streets. Despite the fact that minarets are new, they have come to play an important role in Muslim society.
One thing a minaret does is make a mosque very identifiable. In Muslim cities, communities often arise around mosques, with people frequenting a specific mosque and viewing its minaret as a comfortable and familiar feature in the neighborhood. Travelers sometimes find themselves using minarets as orienting landmarks, since they often tower over surrounding architectural features, making them very easy to find. The competing calls to prayer blaring out from various minarets with the assistance of speaker systems can also be quite a thing to hear.
Many mosques have more than one minaret, and the minarets are often beautifully carved, painted, and tiled, making them works of art as well as functional architectural features. Just like Christian churches, mosques have subscription funds and hold fundraisers to restore their minarets and build new ones, and particularly wealthy Muslims may donate the construction of a minaret to their mosque as an act of faith.
In the hot desert countries which many Muslims call home, the minaret also helps to ventilate the mosque, acting as an air shaft to suck hot air out. These graceful spires are often latticed, promoting circulation, and topped with inventive domes and other architectural features to make them particularly distinctive. The practice of erecting tall spires on places of worship seems to be common to many faiths; you could view it simply as advertisement, and a desire to get closer to God.