Short answers, pulled from the story.
Theravada is the oldest existing school of Buddhism, preserving the Buddha's teachings in the Pali language for over two millennia. This tradition derives its name from the ancient Indian Sthavira nikaya, one of the earliest divisions of the Buddhist community. The school's adherents, called Theravadins, maintain a version of the Dhamma that they believe is the most authentic and closest to the original words of the Buddha.
The Pali Canon was committed to writing for the first time in the 1st century BCE. This event occurred when Theravada Buddhism was well established in the main settlements of the Kingdom of Anuradhapura. The recension of the Tipitaka which survives today is that of the Sri Lankan Mahavihara sect.
Theravada became the official religion of Sri Lanka, Myanmar, and Cambodia, and the main dominant Buddhist variant found in Laos and Thailand. The school spread to Southeast Asia where it became the dominant form of Buddhism, with Theravada becoming the cultural and religious backbone of the region. In the 15th and 16th centuries, numerous Hindu and Mahayana temples in Cambodia were transformed into Theravadin monasteries.
Figures like Anagarika Dhammapala, Migettuwatte Gunananda Thera, and Hikkaduwe Sri Sumangala Thera were central to the Sri Lankan Buddhist revival. In Burma, King Mindon Min was known for his patronage of the Fifth Buddhist council in 1871 and the Tripiñaka tablets at Kuthodaw Pagoda. In Thailand, King Mongkut and his successor Chulalongkorn were especially involved in centralizing sangha reforms.
Central concepts include the doctrine of action (karma), a related doctrine of rebirth, the Four Noble Truths, and the Noble Eightfold Path. Meditation is categorized into two broad categories: Samatha bhavana, or calming, and Vipassana bhavana, or investigation and insight. The ultimate goal of the practice is to achieve mundane and supramundane wisdom, leading to the direct apprehension of Nibbana.