Karma means deed or action. It is the law or principle of actions and activity. It covers ethical intent as well as physical actions.
Simply put - what we are, so have we done; what we do, so we become.
From the above statement it can be seen that Karma is the law of cause and effect. While this is true, Karma is not simple. Our volitions and intentions also have effects. The causes are not passive actions, but ones that are intended.
Karma is often described in a linear way. This is true for some activities such as the life cycle of a tree or flower. Starting from the life force of a seed, a seedling develops, then a young plant, growing to full maturity, and then decaying. Karma is also the process of becoming. Old forms drop away as new ones appear. This can be seen in such examples as ourselves, families, countries and civilizations.
Karma is complex and subtle. Many causes may give rise to an effect which arises when conditions are ripe. Parents may intend for their children to have good schooling, but the children must be capable, a school must be available, etc. These also become causes before the effect can appear. One cause may have many effects, rippling outwards. If one spouse is angry at their partner, then unhappiness of the spouse may result, yet also the angry one may become ill, the spouse may 'take it out' on others, etc. Thus each thing or phenomenon is conditioned by complex interactions of causes and effects.
Karma is occurring at many levels. The life force of the whole universe is moving and unfolding. So to are each individual phenomenon, ourselves and all things. Also groups of various sorts, families, clubs, countries, schools, and cities. Each level exhibits particular effects. We may be happy or sad as an individual, but our school or country can also exhibit that characteristic. There may be primary and secondary causes. The prime cause may be a tree or flower. Secondary causes may include the amount of rain, sun or shade, the quality of the soil. These secondary causes effect the growth and development. Sometimes the effect is long running, sometimes short. A man or a woman appears for a physical life. A feeling of happiness may last a few seconds. Causes take differing times to ripen, some a long time, some instantly. Initial strong causes, slowly ripening, may have their effects modified by intervening causes.
Karma is not fate or destiny. This is a rigid and linear view. Cause and effect are dynamic. Effects are always changing with the circumstances. How a phenomenon appears or becomes is continually shaped by the changing circumstances, which, in turn, are the effects of past causes and causes of current and future effects. Everything is inter-connected. Any action of any thing affects everything. The actions of everything affect each individual thing.
So, how should we act and respond?
We can intend and do actions that help ourselves or help others. Actually, to help others is to help our own development. It brings out the wholesome heart in us. If our intent and actions are only to help ourself then later this will rebound on us, our selfish acts have effects on everyone. A selfish parent may think they create good effects for themselves. However, effects are also created in the partnership and family. Friction may result, and this gives rise to further effects. Likewise a selfish family may cause friction at school, in the neighborhood, etc, and it may receive poor karma as effects of its effects on its surroundings. We are all inter-connected. Buddhism contains Hinayana and Mahayana. A scholar or outsider may see these as schools of Buddhism, perhaps belonging to particular countries. But a practitioner of Buddhism has both Hinayana and Mahayana practices. These are to help develop ourselves and to help others. Both are important, and are inter-connected. We develop ourselves to become free of inner vexations and to be unaffected by unhelpful outer influences. Our real potential arises when we help others.
Usually Karma is not spoken of as 'good karma' and 'bad karma'. There are wholesome and unwholesome intent and volitions. Unwholesome intent is one rooted in greed, anger/hate and delusion. Wholesome intent is rooted in generosity, love, clarity/wisdom.
There is no need to ask 'why?' in terms of Karma. (Why did my child have an accident?) It is more helpful to ask how to expiate the Karma that has bought it about and not to cause further incidents. There is no need for anger or resentment at what ripens in our Karma. Past Karma must be used up, worn down. This does not mean to act out one's Karma, but to see and acknowledge the thoughts and impulses that arise in us. These thoughts and impulses are effects from the past. We can let them be without generating actions based on them. In this way old karma plays out without unwholesome effects. In the meantime we can work hard to produce wholesome intents, volitions and actions.