Diwali, the festival of lights, is one of the most popular holidays in India and especially for Hindus.

It is a celebration of good over evil and is observed across all faiths for five days with gatherings of prayer, feasts and fireworks.

The holiday gets its name from the word “deepavali”, Sanskrit for a series of lamps. It may have its origins in harvest festivals that date back more than 2,500 years.

This year the main holiday is Sunday, but celebrations start days earlier. More than a billion people will celebrate Diwali across South Asia and the Indian diaspora.

Here are five things you should know about Diwali:

What celebrates Diwali?

The festival marks the triumph of good over evil, knowledge over ignorance, light over darkness and new beginnings associated with the Hindu New Year.

It is celebrated in the Hindu month of Kartik, which usually falls between mid-October and mid-November.

For Diwali – which coincides with the new moon, the darkest night of the lunar cycle – candles and clay lamps called diyas are lit in homes and streets everywhere.

Other details may vary depending on where the holiday is celebrated, but all celebrations include lights, fireworks, feasts, new clothing and prayers.

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Who celebrates Diwali?

The holiday, which has become both religious and secular, is celebrated by Hindus, Sikhs, Jains and some Buddhists.

In northern India, it is based on the Ramayana, where Rama’s people light diyas to accompany him, his wife Sita and his brother Lakshmana on a triumphant journey home after 14 years in exile. Many people dedicate the holiday to special prayers to Lakshmi, the goddess of prosperity, in the hope that she will bless them.

In South India, it honors another story of exile from the epic Mahabharata, the victory of Lord Krishna in destroying the demon Naraka, who was said to have imprisoned women and tormented his subjects. Here, many take an early morning bath with warm oil to symbolize bathing in the holy Ganges River as a form of physical and mental cleansing.

Gambling is a popular tradition as it is believed that whoever gambles on Diwali evening will achieve success throughout the year.

And in Singapore, in the run-up to Diwali, a silver chariot carrying the goddess Sri Drowpathai Amman is pulled through the streets by the Sri Marjamman Temple, which also hosts Theemithi, a ritual in which men walk on burning charcoals.

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How is Diwali celebrated?

This year the main holiday falls on Thursday, October 31st, but there are five days of celebration in total.

The first day, Dhanteras, is often a preparation day where people clean their houses or make decorations.

The second day, Naraka Chaturdasi, is for decorating houses with lamps and marks the killing of the demon Narakasur.

On the third day, Lakshmi Puja, families gather to celebrate the goddess Lakshmi with prayers, feasts and fireworks.

On the fourth day, Govardhan Puja, friends and relatives come to visit with gifts.

On the fifth day, Bhai Dooj, brothers visit their married sisters.

How do you decorate for Diwali?

In India, elaborate decorations called rangoli are often painted on the floors of houses to welcome gods and goddesses and ward off evil spirits.

They are made from chalk and powder or from turmeric, rice, flour or lentils and can be geometric or with religious and floral patterns. The word comes from Sanskrit Rangavalli or “color rows.”

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What other ways do you celebrate Diwali?

The holiday is also a time to buy new clothes, gold and jewelry, and kitchen utensils. Holiday sales are common.

How do you greet someone on Diwali?

Here are some suggestions on how to greet someone celebrating during Diwali:

• “I wish you and your family a happy and prosperous Diwali.”
• “May this festival of lights bring happiness and prosperity to your home.”
• “May the splendor of diyas illuminate your life with happiness and success.”
• “Sending you warm wishes for a sparkling and joyful Diwali celebration.”
• “I wish you a celebration full of laughter, lights and love.”
• “May the divine light of Diwali spread peace, prosperity and good health.”
• “May Lord Ganesha and Goddess Lakshmi shower their blessings on you.”

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How is Diwali celebrated in other faiths?

Buddhists, Jains and Sikhs have their own Diwali stories.

Jains celebrate Diwali as the day of Lord Mahavira, the last of the great teachers, who achieved Nirvana – the state of liberation from the cycle of birth, death and rebirth.

Sikhs celebrate Bandi Chhor Divas – a day that overlaps with Diwali – to commemorate the release of Guru Hargobind, a revered figure of the faith who was imprisoned for 12 years by the Mughal emperor Jahangir in the 17th century.

Buddhists consider the day to be the day on which the Hindu emperor Ashoka, who reigned in the third century B.C. BC, converted to Buddhism.

The Associated Press contributed to this article.

Nick Jonas and Priyanka Chopra had a very special Diwali this year. The couple celebrated the Festival of Lights with their nine-month-old daughter Malti Marie.