What is Conscience?

This is what Wikipedia says about conscience:-
“Conscience is an ability or a faculty that distinguishes whether one's actions are right or wrong. It leads to feelings of remorse when one does things that go against his/her moral values, and to feelings of rectitude or integrity when one's actions conform to our moral values. It is also the attitude which informs one's moral judgment before performing any action.”

Commonly used metaphors refer to the ‘voice of conscience’ or ‘voice within.’
Looks quiet straight and simple, but as we go on escavating it, the more complex it becomes, and we find ourself in the middle of desert with questions like:-

What defines conscience?
Is it constant for everyone or effected by environment?
How does one can listen to what his conscience is saying?
How one can decide if his decision was correct to his conscience?
Is the decision taken according to it is always right or can there be a correct decision that is against the conscience?

Conscience is a result of ‘Karuna’ or compassion and it is not dependent on your environment and upbringing.
Karuna is a Sanskrit word and is basis of Hinduism, Buddhism and Jainism and have got much broader context than its English translation. It is a sense of belonging to the universe and realization of the fact that we all are one, lets see a simple example that if you do not throw stone on a street dog thinking it would hurt it, as it would hurt me then it’s the karuna that’s working behind.

So you conscience will always speak what adheres to Karuna, as with the above instance and help us to take the right path.
But is it that simple, well not always, consider a soldier who is on the frontier fighting against the enemy, now this man is really walking on sword, on one hand the person in front of him is also a human, having a family, kids and he has not even personal rivalry with him, how he can kill him, and on the other hand that person is enemy of the country, and his duty’s call is to kill him.
So what does conscience says here? There should be no war at all, but that is not the case here. Now do what? Do the duty. Then what happened to compassion? Well at first it might seems to go against karuna, but actually not because the suffering could be for much larger number of people if he opt for the other way. Follow the path that is beneficial for more people. Follow your conscience.

Hence the decision taken according to the conscience will always be good and vice versa because it would be the decision for the humankind.

As Simon Soloveychik, a famous Russian philosopher says, conscience is a common, one for all, knowledge about what good is and what evil is for humankind. Not for a man, not for his time, not for a group of men, but for humankind as a whole.