There is two understandings of what karma means, the religious meaning and the non religious spiritual meaning.
You can not truly love others until you love yourself first, and that is done by forgiving yourself and at least making a higher percentage of the right choices in each incarnation, in other words always bettering your souls journey rather than continue to degrade your souls journey through each incarnation, karma is like a energy that carries from one incarnation to the next, once a soul has completely clear karma, the soul then remembers all past lives after death, or in the case of some people like Jesus, while still in the physical form.
There is no controlling judgmental entity like this one God religions follow worship and fear of being judged, you judge yourself when you think a God judges you, if you fear God you fear yourself, because God is all, nothing else exists, as we are all God.
