The concept of karma arises from the fact that everything in the universe is a product of interdependence. There is nothing that is not dependent on others for its existence. Interdependence is the nature of our existence. As I understand, karma literally means action in Sanskrit. Our own thoughts and actions translate into our being. If we perform good deed, then we get good results. If we do a bad action, then we have to bear the result for the bad action. It is like if we sow rice seeds in the soil, we will be able to harvest rice only and we cannot expect maize sapling to germinate. As we commonly perceive, Karma is not something like a predetermined power that controls us. It is the consequences of our own thoughts and actions that we perform. In this way karma is in our own hand.
In Buddhism, karma is classified into three different types. The first class of karma gives immediate results. For example, I said something bad to my friend in the morning. As a result of this, my whole day went in a bad mood. This is the consequence of my own karma. The second class of karma gives result in the immediate next life. For instance, in this life you donated huge proportion of your wealth to charity. As a result of this good karma, you are born into a rich family in next life. And the third type of karma gives result in the lives after many life forms. It needs conditions to assemble for a particular karma to take effect.
Understanding the concept of karma has huge benefit. If by understanding the law of karma, we make wise decisions regarding our thoughts, speech and actions, then we accumulate good karma. Good karma will definitely lead to good results one day or the other. On the other hand, if we do not think about our thoughts and actions and mindlessly go about doing one immoral actions after another, then we create a huge mass of bad karma. Eventually, we and only we have to bear the consequences of the bad karma. So while we are endowed with this brilliant human mind, it is better to be mindful and make good karma as our priority.