Karma means action. It is also the reaction that follows on an action. The process of compensation for any given feeling, thought or deed is completely automatic. Karma in its sense of law keeps the cosmos in balance and harmony. Life in cosmos is severely restricted. On some planets more than others. Here there are both physical and personal limitations on what you can do. Karma, however, is your unrestricted power of choice, and it makes sure that for every choice you make there will be just consequence. The law of karma is often expressed with this quote: "As you sow you shall reap".
Karmic Fruits
Good seeds produce good fruits, while evil seeds produce evil fruits. That said, karma does not concern itself with good or evil. It simply returns what has been given. To make it slightly more complicated, karma is only produced when pain is nourished and joy quelled. If instead joy is nourished and pain quelled no karma will be produced. The following offsite link explains this further: Buddhist Law of Karma.
Resolution of Karma
All karma must be experienced or resolved. Karma can be resolved through understanding. Karmic seeds understood as to their consequence as they are sown as well as to their result as fully developed fruits will be resolved. Unresolved karmic seeds will develop into karmic fruits providing experience equal to that sown. Karmic fruits understood as to their cause will bring evolution away from action.
Reaction to Change of Cosmic Position
When trying to move up the ladder of cosmic existence you will be confronted with experiences trying to keep you down. Conversely when falling down you will face experiences trying to move you back up. Only if you insist on changing your position it will indeed be changed. After the change a new status quo will be established.
Karma and Fate
Karma in the sense of reaction is different from fate in the way that fate involves your total experience, while karma is produced from action alone and not from creation or meditation.