According to the biblical story, Abel was a shepherd and Cain worked the soil. Each brought an offering to the Lord from fruits of his labor. Abel's sacrifice was accepted by the Lord, but Cain's offering was rejected. Cain, in his jealousy, killed his brother. This is the first recorded incident of murder in the Torah.
Explanations of this story are usually sought in a traditional conflict between agriculture and nomadism. Thus the preferential treatment accorded Abel's sacrifice is seen as reflecting a supposed pastoral ideal in Israel. The narrative, however, does not in any way support the existence of such an ideal, nor is there any denigration of farming. On the contrary, working the land seems to be considered man's natural occupation (Gen. 2:15). The antithesis between the brothers is therefore less one of occupations than of qualities of offerings. Whereas Cain's offering is described simply as "of the fruits of the soil," Abel is recorded as having brought "of the choicest of the firstlings of his flock." The story, however, seems to be abbreviated. It lacks any description of the initial motivation and the occasion for the sacrifices and it fails to give the reasons for the rejection of Cain's offering. Neither does it explain how the Lord's response became known to the brothers. The etymology of Abel's name is not clear. There may be some intended connection with hevel ("breath, vapor, futility"), symbolizing the tragic brevity of his life (cf., e.g., Eccles. 1:2), though for some reason the derivation of the name is not given, as is the case with Cain. There may also be some relation to the Akkadian aplu or ablu ("son"), parallel to the usage of the names *Adam and *Enosh .
Source: Encyclopaedia Judaica, The New Jewish Encyclopedia, Navigating the Bible II
N.M. Sarna, Understanding Genesis (1966), 28–32; E.A. Speiser, Genesis (1964), 29–33; U. Cassuto, Mi-Adam ad No'aḥ (1953), 131–9.