A Bhikkhu (PÄli) or Bhiká¹£u (Sanskrit) is an ordained male Buddhist monastic. A female monastic is called a Bhikkhuni (Skt: Bhiká¹£uá¹Ä«) Nepali: à¤à¤¿à¤à¥à¤·à¥à¤£à¥). The life of Bhikkhus and Bhikkhunis is governed by a set of rules called the patimokkha within the vinaya's framework of monastic discipline. Their lifestyle is shaped to support their spiritual practice, to live a simple and meditative life, and attain Nirvana. In the Vinaya monastic discipline, a man under the age of 20 cannot ordain as a bhikkhu but can ordain as a samanera (à¹à¸à¸£); the female counterpart is samaneri.
What you are looking at is a gathering of 100.000 Theravada Buddhist monks who are ‘praying’ for a better world. The reason why I am adding the apostrophe is because they are not literally praying, there is no deity to whom they address. This happened at a temple in Bangkok.