Fasting during Ramzan is one of the five pillars of Islam, along with the Muslim declaration of faith, daily prayer, charity, and performing the hajj pilgrimage in Mecca. It is a time to detach from worldly pleasures and focus on one's prayers. The fast is intended to bring the faithful closer to God and to remind them of the suffering of those less fortunate. Muslims often donate to charities during the month and feed the hungry.
Fasting means abstain from eating and drinking from dawn to dusk for the entire month of Ramzan, with a single sip of water or a puff of a cigarette considered enough to invalidate the fast (some time not even your own saliva)