Hebrews 11:4

By faith Abel offered God a better sacrifice than Cain did. By faith he was commended as a righteous man, when God spoke well of his offerings. And by faith he still speaks, even though he is dead. 

Any offering we give to honor GOD is just a display of our faith. When we offer from the heart, with no ulterior agenda, such as public offerings to raise one's status or as a trade for blessings. Abel offered to GOD through faith that he must have leaqrned from Adam. It was an offering of living faith. He truly believed in GOD's instructions and acted on them.

Caine, on the other hand, heard the same instructions but didn't act, thus his faith is dead faith. Dead faith is displayed through people who are instructed in GOD's commandments but fails to do submit and act on them. He is essentially infoemed but not conforming. Through living faith we are informed and we submit and practice GOD's commandments and that leads to growth.