What is a mosque's most important function?

The idea of the mosque is to assist Muslims on their mission of purifying the world. In essence, the mosque is related to all aspects of the life of devout Muslims and is the vehicle by which Muslims engage in the affairs of the world, both as individuals and as communities.

Explanation:

Of all Muslim institutions, the mosque is the most important place for the public expression of Islamic religiosity and communal identity. A mosque is a physical manifestation of the public presence of Muslims and serves as a point of convergence for Islamic social and intellectual activity.