Karma - basically this means the actions you perform through your mind, body & words. If the thoughts, actions & words are good they are good karma. If the thoughts, actions & words are bad they are bad karma.
In another way this is also can identify as the cause. The effect is always according to the cause. That's how most of the time we happen to say, it's because of karma this is happening etc… etc…
The force made by previous karma decides the time period for the effect.
If you throw a ball to the sky it's moving higher & higher until it has the force which you have given to it. When the power of force finishes its stop going higher and begins to move downward / falling. Likewise the karma - The actions, words & thoughts also produce a force / energy and as long as that energy exists the effect also exists.
So, this basic idea of karma will be a help for you to get a clearer idea of the below explanations. I will discuss about karma more in cause & effect theory & meditation so you get more understanding about the Karma.
And also I would like to add how the past karma aligned and how it is possible to transcend the past karmas.
We already created load of karma which is enough to hold us to the existence of zillion years. Then how we can transcend these karmas to cease the existence? If I explain through an example it will be easy to understand.
A sparkler is a type of hand-held firework that burns slowly while emitting colored flames, sparks, and other effects.
The "classic" type of sparkler consists of a stiff metal wire approximately 20 cm (8 inches) long that has been dipped in a thick batter of slow-burning pyrotechnic composition and allowed to dry.
(The composition contains these components, one or more of each category: Metallic fuel, mandatory to make sparks; size of particles influences appearance of the sparks, Aluminum or magnesium or magnalium, producing white sparks, Iron, producing orange branching sparks, Titanium, producing rich white sparks, Ferrotitanium, for yellow-gold sparkles, Additional fuel, optional, modifying the burning speed, Sulfur, Charcoal, Oxidizer, mandatory, Potassium nitrate, Barium nitrate, Strontium nitrate, Potassium perchlorate, more powerful but potentially explosive, Optional pyrotechnic colorants, for colored flames, chlorides and nitrates of metals, e.g. barium, strontium, or copper, Combustible binder, holding the composition together, Dextrin, Nitrocellulose, The colored spot on the top of each rod indicates the color of the sparkles emitted when ignited)