Sīla: 'morality', 'virtue', is a mode of mind and intention cetanā manifested in speech or bodily action see: kamma. It is the foundation of the whole Buddhist practice, and therewith the first of the 3 kinds of training sikkhā that form the 3-fold division of the 8-fold path see: magga i.e. morality, concentration and understanding.
Buddhist morality is not, as it may appear from the negative formulations in the Sutta-texts, something negative. And it does not consist in the mere not committing of evil actions, but is in each instance the clearly conscious and intentional restraint from the bad actions in question and corresponds to the simultaneously arising intention.
Morality of The Noble Eightfold Middle Path, namely, Right Speech, Right Action and Right Livelihood, is called 'genuine or natural morality' pakatisīla as distinguished from the external rules for Bhikkhus or laymen, the so-called 'prescribed morality' paññatti-sīla,, which, as such, is kammically neutral.
What now is kammically advantageous morality kusala-sīla It is the advantageous bodily action kāya-kamma see: kamma, advantageous verbal action vacī-kamma kamma, and also the purity with regard to livelihood which I call morality; M. 78. Cf. magga 3-5.
For the 5, 8 and 10 rules, see: sikkhāpada Further cf. cāritta and vāritta-sīla.
The 4 kinds of morality consisting of purification catu-pārisuddhi-sīla-sīla are: 1 restraint with regard to the Bhikkhus' Disciplinary Code, 2 restraint of the senses, 3 purification of livelihood, 4 morality with regard to the 4 requisites of the monk.
- Restraint with regard to the Disciplinary Code pātimokkha-samvara-sīla, Here the Bhikkhu is restrained in accordance with the Bhikkhus' Disciplinary Code, is perfect in conduct and behaviour, and perceiving danger even in the least offences, he trains himself in the rules he has taken upon him; A. V, 87,109,114, etc..
- Restraint of the senses indriya-samvara-sīla Whenever the Bhikkhu perceives a form with the eye, a sound with the ear, an odour with the nose, a taste with the tongue, an contact with the body, an object with the mind, he neither adheres to the appearance as a whole, nor to its parts. And he strives to ward off that through which evil and disadvantageous things, greed and sorrow, would arise, if he remained with unguarded senses; and he watches over his senses, restrains his senses; M 38.
- Purification of livelihood ājīva-pārisuddhi-sīla It consists therein that the Bhikkhu does not acquire his livelihood in a way unbefitting to a monk.
- 4: Morality with regard to the 4 recquisites paccaya-sannissita-sīla It consists therein that the Bhikkhu is guided by the right mental attitude when making use of the 4 requisites: robes, foodfood, dwelling and medicine.;Wisely reflecting he makes use of his robes... merely to protect himself against cold and heat, etc. Wisely reflecting he makes use of his foodfood... merely as a prop and support to this body. Wisely reflecting he makes use of his dwelling... merely to keep off the dangers of weather and to enjoy solitude. Wisely reflecting he makes use of the necessary medicines, merely to suppress feelings of sickness that arise, and to reach perfect freedom from suffering; cf. M. 2.
About these 4 kinds of morality, Vis.M I gives a detailed exposition.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.