Sila is a good practice which makes any observable one well and beneficial. It keeps the devotee from killing, stealing, sexual misconduct, using intoxicants, i.e. all bad deeds. It also keeps one from telling lies, making mischief, using abusive words, indulging in trivial talk, i.e. all evil words.
Sila has the two main grades, namely Gahattha-Sila and Bhikkhu-Sila. The former is meant for the lay people and the latter for the monks. The lay person observes lower grade and the monks pay attention to the higher grade.
Moreover, the precepts are also divided into two classes, viz: Caritta Sila and Varitta Sila. Every Buddhist should perform the moral instructions i.e. ethical rules stated by the Buddha, because these are Caritta sila. Caritta sila are mostly regarded in positive forms such as sufficient dutiful help towards parents, teachers, wives, children, respectful elders, the needy, the poor, patients; observance of good manners and etiquettes, etc.
Similarly everyone should avoid all the misdeeds shown by the Buddha as the precepts. All of bad actions recognized as Varitta sila are in negative forms such as killing, stealing, misconduct in sex, lying, use of intoxicants, etc. Both the Caritta and the Varitta silas always have relations with everybody. But most of us used to live to be forgetful of the precepts.
In two classes of sila, the first one for the monks has four types, known as:  Patimokkha samvara sila,  Ajiva parisuddhi sila,  Indriya samvara sila, Paccaya sannissita sila. The second one for laymen consists of  Panca sila,  Ajivatthamaka sila,  Atthanga Uposatha sila,  Navanga sila.
The two silas [1 & 2] in the latter are minimum silas for a Buddhist. So they are called nicca silas. Nicca means always. A real Buddhist must keep either  or  silas always. Panca sila concerns with one's morality to take five vows; Ajivatthamaka sila requires one to refrain from earning a wrongful livelihood for eight vows. In Burma, 8th waxing, full moon, 8th waning, full waning days are generally fixed for keeping Uposatha sila.
There are also different levels of sila. Those are:
 five precepts (panca sila),
 eight precepts (uposatha sila or atthanga sila) or asceticism,
 nine precepts (navanga sila),
 ten precepts (dasa sila) for novice (samanera sila) and nuns (samaneri sila), and
 Patimokkha (Upasampada sila) [the 227 rules for a fully-ordained monk (bhikkhu); the 311 rules for a higher ordained nun (bhikkhuni)] or Vinaya pitaka.
Lay persons (puthujana) generally observe the five precepts that are common to all Buddhists for their lives. When they wish, they can decide to undertake the atthanga sila.
The panca sila is the first step to the Buddhist training. Then it is the most important to be a true Buddhist. One should not be a nominal Buddhist who has been born and grown up in a Buddhist family. If this were so, it will be in vain. Therefore, to practise panca sila is essential for all Buddhists as their lifelong companion. On this account one has been a true and entirely pure Buddhist.
The panca sila is not taken in command of oneself. But the Buddhists live with these training rules for a better life. By this way everyone concentrates his mind with peace, without worries, and then under this condition can also practise meditation well.
Posted by Nyan U