In general terms what Judaism means by “sin” is that being human is a matter of choice and that wrong choices conduct to de-humanization.
Judaism, for sure, has an unambiguous understanding of who a human being is and consequently, who is a “failed” human being.
Society has made sure to take off the back of the concept of sin those de-humanizing acts that affect it. Jails are populated by human beings who have failed to live as humans among humans.
“Sin,” as Yom Kippur understands it in our day and age, on the other hand, throws the spotlight on those actions that society does not penalize, or at least does not penalized with jail.
Many of those acts are unintentional, “sins committed by ignorance.” Others are committed by inaction.
The Talmud, in fact lays down the principle that a person is held accountable for the sins of his/her family, or community, or even "of all humankind" when he or she fails to employ the influence he or she commands for the correction of abuses.
In a sense, the relevance of the concept of “sin” today is its recognition of those personal acts that alienate a person from his, her humanity.
The “sin” of human beings is failing to live as human beings, caring for each other and for making the world a better one for the next generations. According to Judaism that’s the reason a human being comes into the world.
The late conservative rabbi Harold Schulweiss, for instance, urged to “take our fast from Yom Kippur into the streets and into the marketplace, to use our voice to pierce the callousness of society. ”
Characteristic of the prayers of this Holiday is the confession of sins as expressed in the litany “al het,” repeated 8 times during the whole day.