Orlog, much like Wyrd, is a fundamental concept in Norse practices. It is sometimes referred to as a "primal layer" due to the fact it is mentioned in lore that the Norns are responsible for making a "primal layer", or a series of strands determining fate. It differs from Wyrd in that it is your moral momentum: which can be altered, but is not easy to change.
It was believed that people's souls consisted of a part inherited by their parents and ancestors (which would be passed down through heritage) and a part that was influenced and created through the persons own actions throughout one's lifetime. This is different from the concept of karma, in that there isn't necessarily the idea of "good and bad": it states that the things you tend to do will tend to happen to you, regardless. For example: "If you tend to be honorable, you will generally find yourself surrounded by honorable people, who treat you honorably"(Shetler)
Part of orlog is inherited- it is believed to have been passed down through your ancestors. The majority of this part would come from your parents, a lesser amount from your grandparents, and a lesser amount from your great-grandparents, and so on all the way through your heritage. This part of orlog would also be passed down from you to your children. In a way, part of our orlog is not up to our making: it has already been made and is given to us. But we are still responsible for the actions we take in responding to them. Picture a web. This web is Wyrd.
(a link to my article on wyrd: http://www.spellsofmagic.com/read_post.html?post=380456)
Wyrd is the general web laid out representing our fate. Orlog would be the threads, and layers of threads, making this web possible. Everything is interconnected in this way, making both orlog and wyrd essential to each other. This concept of a part of you being inherited stresses the importance of family in these types of beliefs and practices, as well as makes the consequences of your actions and orlog more apparent. Doing something which is undesireable, or "bad", will effect the rest of your family in a negative way.
The part of orlog that is determined by you is built up through the actions and behaviors you have shown throughout your life, and is a type of moral momentum. Changing this moral momentum is not an easy thing to accomplish. You cannot "get rid of" past wrongs by attempting to atone for them- they are still there regardless. However, sufficient atonement and actions that are considered "right" could equal out the balance. And though the wrongs would still be there, the "right" would make it even once again. The issue is that "good/bad" and "right/wrong" are hard to determine in Norse practices. There isn't a giant list of things you do that are considered bad or good. It's decided through your actions. What determines good/bad, right/wrong are behaviors and actions that make you a leader, companion, kinsman, partner- or just someone desirable to others. In Asatru, this goes so far as to say you strive to be desirable to the Gods. This is how the Norse determine(d) ethical systems, all these things are considered: the effect on family, the effect on social desirability, one’s own morals, the Gods opinions, etc.
Norse see the "correct" and "right" actions to make us desirable in general. And as you can imagine, this leaves plenty of room for flexibility. The Norse understand that there are situational occurrences which call for certain action, that may be against the virtues and behavioral ethics they strive to uphold. Situations can change the perspective of things. “Taking [unfavorable] actions on behalf of those to whom you have professed loyalty to builds an orlog that is filled with a likelihood that they will similarly defend you, if called on to do so.”(Shetler)
There is a certain type of "reward" or "punishment" one can receive. Because there is no forgiveness under these concepts, one would have to strive to atone and make up for the past wrongs by balancing them out with "right" actions. Depending on your orlog, you may go to one of the various halls or have the halls closed to you. However, most tend to not think too much about the afterlife. The "here and now" is thought to be the more important aspect, and whatever comes will come.
Essential Asatru by D. Paxson
Living Asatru by Greg Shetler
Nordic Religions In the Viking Age by University of Pennsylvania Press