Friday is the day of the weekly congregational prayer. Muslim men are required to attend, and women are welcome. It replaces the midday prayer and includes a sermon (khutbah) by the imam.
The fuller answer
The Quran tells believers that when the call to prayer is made on Friday they should hasten to the remembrance of God and leave trade. After the prayer, they may go back to their work. In many countries, it is the day when Muslims gather, dress well and meet neighbours.
The sermon speaks on faith, character and community matters, and is often given in the local language. Friday is not a day of rest like the Sabbath: Muslims may work before and after the prayer. Non-Muslims are usually welcome to visit a mosque.
O you who have believed, when [the adhan] is called for the prayer on the day of Jumu'ah [Friday], then proceed to the remembrance of Allah and leave trade. That is better for you, if you only knew. And when the prayer has been concluded, disperse within the land and seek from the bounty of Allah, and remember Allah often that you may succeed.
This answer follows the mainstream Sunni understanding and is general learning, not a fatwa. Where Muslims differ, the answer says so. Have a question of your own? Write to us.