Yamas and Niyamas are two of the eight limbs of Yoga enumerated by Patanjali.
Yama means restraint and includes ahimsa (non-violence), satya (truthfulness), asteya (non-stealing), brahmacharya (preservation of sexual energy and cultivation of it) and aparigraha (non-covetousness).
Niyama means observance and includes saucha (purity and cleanliness), samtosa (contentment), tapas (heat/focus/austerity), svadhyaya (study of scriptures and self) and isvara pranidhana (surrender to the divine).