“The use of mantra or the repetition of certain phrases in Pali is an extremely common form of meditation in the Theravada tradition. Simple mantras use repetition of the Buddha’s name , “Buddho,” [actually “Buddho” is a title rather than a name] or use the “Dhamma,” or the “Sangha,” the community, as mantra words. Other mantras that are used are directed toward developing loving kindness. Some mantras direct attention to the process of change by repeating the Pali phrase that means “everything changes,” while other mantras are used to develop equanimity with phrases that would be translated, “let go.”
Very often mantra practice is combined with breathing meditation, so that one recites a mantra simultaneously with in-breath and out-breath to help develop tranquility and concentration. Mantra meditation is especially popular among the lay people. Like other basic concentration exercises, it can be used simply to still the mind or it can be the basis for an insight practice where the mantra becomes the focus of observation of how life unfolds, or an aid in surrendering and letting go.
– Jack Kornfield, Living Buddhist Masters