In Christianity, a sin is an act that goes against what God wants.
Sins can be against other people (such as murder), against animals, or against God (such as worshipping false gods). Not all societies have the same idea of sin.
The idea of sin is central to Christianity. Christianity’s central message is about Jesus Christ redeeming sins through his sacrifice on the cross.
Some Christianities include the idea of original sin. This is the idea that every human being is born with sin ever since Adam and Eve were expelled from the Garden of Eden.
Text adapted from Simple English Wikipedia, Creative Commons Attribution-ShareAlike License 4.0.
Dzieje objawienia boskiego w Starym i Nowym Zakonie by Polona Digital Library via Wikimedia Commons, Public Domain.