Merits are the special energy gained or ability developed by devotedly following a righteous lifestyle, while sins are generated by those acts which are responsible for someone else’s decline.
This article explains why people become Serial killers and mass murderers
While we may have given and received gifts all our lives, we may not be fully aware of the spiritual implications of giving and receiving gifts.
After we die on Earth, we (i.e. our respective subtle bodies) go to one of the various subtle regions of the Universe depending on our spiritual level and merits and demerits.