The Five Precepts constitute the basic code of ethics undertaken by "lay followers" of Buddhism. The precepts in all the traditions are essentially identical and are commitments to abstain from harming living beings, stealing, sexual misconduct, lying and intoxication.
Undertaking the five precepts is part of both lay Buddhist initiation and regular lay Buddhist devotional practices. They are not formulated as imperatives, but as training rules that lay people undertake voluntarily to facilitate practice.
Additionally, in the Theravada schools of Buddhism, the bhikkhuni lineage died out, and women renunciates practicing Theravadin Buddhism have developed unofficial options for their own practice, dedicating their life to religion, vowing celibacy, living an ascetic life and holding eight or ten precepts. They occupy a position somewhere between that of an ordinary lay follower and an ordained monastic and similar to that of the samaneri. In Thailand, they are called maechi (in Sri Lanka, they are dasa sil mata; the Burmese thilashin are also now found in Nepalese Theravadin Buddhism as well; and in South East England, the Amaravati Buddhist Monastery founded by Ajahn Chah has siladhara.