What is the meaning of the ''You shall not kill'' commandment?

Answer 1

Wrong translation. The commandment actually states "You shall not murder" (Exodus ch.20). In Hebrew as in English, "kill" and "murder" are used to convey separate things.Since the intent of the Hebrew word (רצח) is not the same in all contexts, this verse (among others) illustrates the importance of the Oral Tradition, which clarifies the intent here.
This commandment means that it is forbidden to murder someone. It prohibits us from killing except in valid circumstances such as defending one's own life, or having a court of law sentence a murderer to death.

See also:

The Ten Commandments

Answer 2

The Hebrew word "ratsah" in the 6th Commandment refers to premeditated murder without just cause. However, it can also be used in the sense of manslaughter, as when one kills by mistake, or without intent, like in the case of Numbers 25:11; Deuteronomy 4:42, 19:4, Joshua 20:3-5, and elsewhere. Thus in Hebrew the specific meaning of this word must always be determined by its context. We must always see it in relation to the surrounding statements. In the Commandments it is absolute and the law is conditional…

Sin is a transgression of the Law (1 John 3:4) and there are actually 613 Torah-commandments…the soul that sins it must die is called the curse of the law but actually goes all the way back to the garden and what is really being said is that sin brings forth sickness and death (spiritual death). Next, we have the word "hemit", which carries no sense of guilt or iniquity and is used in the case of righteous capital punishment, or when the killing is the result of an attack from a wild beast, and so on. The root of this word may be related to the word "emet" or truth. We see this usage in Leviticus 20:4; Numbers 35:19-21; Deuteronomy 13:10 and Deuteronomy 17:7. Finally, when God orders the execution or destruction of an individual or group (like when He commands Joshua at the five cities of Canaan), the word "harag" is used (See Genesis 20:4; Exodus 4:23, etc.). This form of killing is used specifically in the prevention of foreseen evils beyond our comprehension. By eliminating these people, God is actually sparing millions of people the pain, disease, suffering, and death that they would have caused. It would be used for example in eliminating an Adolph Hitler. There is absolutely nothing evil in this, in fact it is very good. Therefore, this form of killing is always just, whether or not we finite humans can see the full implications of His doing it.

Answer 3

"Thou shalt not kill" is the sixth commandment.