Abel was a keeper of sheep and Cain was a tiller of the ground.

And in process of time it came to pass that Cain brought of the fruit of the ground an offering unto the Lord.

And Abel he also brought of the firstlings of his flock and of the fat thereof as an offering to the Lord.

And the Lord had respect for Abel’s offering because his offering was from the best of his herd.

But Cain did not bring the best of his crop as an offering to the Lord. Therefore God did not respect Cain’s offering. Cain was very upset and his countenance fell.

So the Lord said to Cain “Why are you angry? And why is thy countenance fallen? If you do well next time will your offering not be accepted? If your offering is not good then sin has fallen at your door and sin will rule over you.”

It came to pass when they were in the field that Cain rose up against Abel his brother and slew him.

The Lord said unto Cain “Where is your brother Abel? And Cain said “I do not know. Am I my brother’s keeper?”

So God said “What have you done? The voice of your brother cries out to Me from the ground. Because you have killed your brother you are cursed. Crops will not grow for you or your descendants. You shall be a fugitive and a wanderer on the face of the earth.

The history of Cain And Abel is told about in Genesis Chapter 4:1-8.