Genesis 4:3-4

Genesis 4:3-4

[3] And in process  of time  it came to pass, that Cain  brought  of the fruit  of the ground  an offering  unto the LORD.  [4] And Abel,  he  also brought  of the firstlings  of his flock  and of the fat  thereof. And the LORD  had respect  unto Abel  and to his offering: 

What is the context of Genesis 4:3-4?