Hundreds of millions of Muslims around the world began fasting on Thursday from sunrise to sunset for the month of Ramadan, a time of contemplation, fortitude and intense worship.Here are some questions and answers about Islam's holiest month and how it's observed:WHY DO MUSLIMS FAST?Fasting is meant to draw worshippers closer to God (Allah) through sacrifice, remembrance and heightened spirituality. It's also meant to be a month of gratitude in which the faithful are reminded of the suffering of those less fortunate.Similar to a detox, fasting is often most challenging at the start, especially when kicking habits like caffeine and cigarettes during the day.Islam calls upon the faithful to also try and detach from worldly pleasures and focus on one's deeds, thoughts and actions.Fasting is seen as a way to physically and spiritually purify. Muslims often donate to charities during the month and feed the hungry. Many spend more time at mosques during Ramadan and use their downtime to recite the Quran.HOW DO MUSLIMS FAST?Muslims must abstain from all eating, drinking or smoking from dawn to dusk each day for the entire lunar month, around 30 days. A single sip of water or a puff of a cigarette is enough to invalidate the fast.Sexual intercourse is also forbidden during the daylong fast, and Muslims are encouraged to avoid gossip and arguments.Read: Tunisians protest for right not to fast during RamadanTo prepare for the fast, Muslims wake in the night for a pre-dawn meal called "suhoor".Often the small meal will include vegetables and fruits, tea, yogurt, dates, and power foods such as beans and lentils. In many cities in the Muslim world, volunteers wake the faithful for suhoor by marching through the pre-dawn streets chanting and beating drums.HOW DO MUSLIMS BREAK THEIR FAST?Muslims traditionally break their fast like the Prophet Muhammad did some 1 400 years ago, with a sip of water and some dates at sunset. After sunset prayers, a large feast known as "iftar" is shared with family and friends. Iftar is a social event as much as it is a gastronomical adventure. Across the Arab world, apricot juice is an iftar staple. In South Asia and Turkey, yogurt-based drinks are popular.Every night of Ramadan, mosques and aid organisations set up tents and tables for the public to have free iftar meals.CAN MUSLIMS BE EXEMPTED FROM FASTING?Children, the elderly and the ill are exempt, as well as women who are pregnant, nursing or menstruating. Travellers, including athletes taking part in tournaments away from home, are also exempt from fasting.Muslims living in the Northern Hemisphere will fast through especially long days this year, with the sun setting as late as 21:00 in cities like London. For those living even farther north, Muslim scholars advise those fasting to adhere to time zones of the nearest Muslim-majority city or country.HOW DO MUSLIM-MAJORITY COUNTRIES OBSERVE RAMADAN:Many Muslim-majority countries curb the sale of alcohol during the month of Ramadan, limiting when it can be sold and to whom. In some countries, people who eat in public during the day can be fined or even jailed, although adherence to Ramadan etiquette by non-Muslims is often a personal choice and not enforced by police.Read: Tunisian sentenced to jail for smoking during RamadanIn the United Arab Emirates, for example, which has large Western expatriate populations in Dubai and Abu Dhabi, restaurants use curtains to conceal customers who eat during the day. In Saudi Arabia, restaurants simply close during the day.WHAT ARE SOME RAMADAN TRADITIONS?Once the start of the holy month is declared, Muslims share greetings such as "Ramadan kareem" and "Ramadan mubarak" via text messages, calls and emails to family and friends.Another hallmark of Ramadan is nightly prayer at the mosque among Sunni Muslims called "taraweeh".Egyptians have the tradition of the "fanoos", a Ramadan lantern that is often the centrepiece at an iftar table or seen hanging in window shops and from balconies. In the Arabian Gulf countries, wealthy families hold "majlises" where they open their doors for people to pass by at all hours of the night for food, tea, coffee and conversation.Increasingly common are Ramadan tents in five-star hotels that offer lavish and pricey meals from sunset to sunrise. While Ramadan is a boon for retailers in the Middle East and South Asia, critics say the holy month is increasingly becoming commercialised.Scholars have also been disturbed by the proliferation of evening television shows during Ramadan. In Pakistan, live game shows give away gifts promoting their sponsors. In the Arab world, monthlong soap operas rake in millions of dollars in advertising.HOW DO MUSLIMS MARK THE END OF RAMADAN?The end of Ramadan is marked by intense worship as Muslims seek to have their prayers answered during "Laylat al-Qadr" or "the Night of Destiny".It is on this night, which falls during the last 10 nights of Ramadan, that Muslims believe God sent the Angel Gabriel to the Prophet Muhammad and revealed the first verses of the Quran.After these intense nights of prayer, the end of Ramadan is met with a three-day holiday called Eid al-Fitr. Children often receive new clothes, gifts and cash.Muslims attend early morning Eid prayers the day after Ramadan. Families typically spend the day at parks, eating in the sunshine for the first time in a month.