It is the second most important Buddhist festival after Vesak; it celebrates a gathering that was held between the Buddha and 1,250 of his first disciples, which, according to tradition, preceded the custom of periodic recitation of discipline by monks.

It is an occasion when Buddhists go to the temple to perform merit-making activities, such as alms giving, meditation and listening to teachings.

[9] Māgha Pūjā day marks an event occurring at the Veḷuvana [th] grove, near Rājagaha (present Rajgir) in northern India,[1][13] ten months after the enlightenment of the Buddha.

The traditional story goes that a meeting was held in the afternoon, that had four characteristics, known as the cāturaṅgasannipāta [th]:[14] Because of these four factors, Māgha Pūjā is also known as the Fourfold Assembly Day.

"[20]Finally, the last stanza is about the path of religious practice:[19] "Not abusing, not injuring, and restraint under the rules of discipline, and knowing moderation in eating, and secluded lodgings, and exertion in respect of higher thought, this is the teaching of the awakened ones.

"[20]According to the traditional Pāli commentaries, the Buddha continued to teach this summary for a period of twenty years, after which the custom was replaced by the recitation of the monastic code of discipline by the Saṅgha themselves.

[23][24] Apart from the religious meaning, Māgha Pūjā also reflects the Southeast Asian agricultural year, as it is celebrated after the harvest.

[38] Monastics and lay devotees will hold processions, light candles, attending preaching and making offerings of food, as well as meditating and Buddhist chants.

[40] Māgha Pūjā is celebrated most extensively in Thailand,[41] but it is a national holiday in most Southeast Asian countries,[42] such as Laos and Myanmar.

[48] Other popular ways to spend one's time in the week of Māgha Pūjā, as found in a 2019 poll by the Suan Dusit University [th] among 5,335 respondents of different ages:[49] At times, special events are also held, such as a recital of the entire Buddhist scriptures and ceremonies for avowing oneself as a Buddhist lay person.

Uraiwan Thianthong [th], the then Minister of Culture, felt this was unnecessary, since "there are quite a lot of occasions" in the Thai calendar to express gratitude.

[48] To what extent Thai people are well informed about Māgha Pūjā is in dispute: in 2017, the National Institute of Development Administration (NIDA) held a poll among 1,250 subjects of diverse backgrounds and found that 58 percent of Thai did not know why Māgha Pūjā was important in Buddhism, and 75 percent did not know it had been branded as a day of gratitude.

On the day, devotees make merit, cook meals for elderly people or their parents, and clean up their houses.

[57] Meanwhile, Prime Minister Hun Sen and the Ministry of Cults and Religion have promoted activities on the day, and education for youths about it.

[43][62] Burmese devotees make merits and meditate during this period, and in Mandalay and the North, sand pagodas are made in honor of the Buddha.

[23][68] In the evening, a procession (Sinhala language: perahera) with approximately 5,000 people and many elephants is held, called Gangarama Navam.

[43] In addition, Māgha Pūjā has become a popular event among Buddhist converts in the West, who consider it a day of exchanging gifts.