It refers to the school of elder monks.
The school uses the Buddha’s teaching preserved in the Pali Canon (only existing complete Buddhist canon) as its doctrinal core.
In Theravada, the ultimate goal is the cessation of the kleshas and the attainment of the sublime state of Nirvana, achieved by practising the Noble Eightfold Path, thus escaping what is seen as a cycle of suffering and rebirth.
Kleshas include states of mind such as anxiety, fear, anger, jealousy, desire, depression, etc.
According to the Theravada tradition, Samatha and Vipassana form an integral part of the Noble Eightfold Path as described by the Buddha. Samatha deals with calming the mind and Vipassana means insight into the three marks of existence: impermanence, suffering, and the realisation of non-self.
Theravada believes in the concept of vibhajjavada i.e., “teaching of analysis”.
Visuddhimagga (The Path of Purification) is the great treatise on Theravada Buddhist school, written by Buddhaghosa in the 5th Century AD in Sri Lanka.
It discusses seven stages of purification (satta-visuddhi) to be followed under Theravada Buddhism to attain salvation.
Pali is the sacred language of Theravada Buddhism.
Theravada is contemplated to be a successor of Hinayana school.
Around 35.8% Buddhists in the world belong to Theravada school.
Other countries following it includes Sri Lanka, Cambodia, Laos, Thailand, Myanmar, etc.