In plain words
In karmas, birth keeps coming about; in karmas, happiness comes about; the world came to have karma, good and ill; happiness and sorrow stand fixed on earth.
Karmānubandhini manuṣyaloke. The world is full of Brahman. The world that is full of Brahman is full of karma. Creation itself is one great karma. Man is part of creation, so man himself is karma. Man means the life-force. The vehicle of the life-force is the body. The body itself is full of karma. Bodies are gained only according to karma. So karma alone is the basis of humanity and of all creation. Karma alone is the root. To recognise the principle of this karma, we must do karmas. To do karmas, we must understand karmas.
Karma is the name for the work that mind, speech and body do. For the doing of karma there are five principles. The first is the body. The second, the doer. The third, the various organs. The fourth, the different actions. The fifth is none other than the Divinity, the principle of life present in them all. Everything happens through the Divine alone. But, unable to recognise this Divinity, relying only on the limbs and organs, they do not carry out the duty of humanity; hoping for the fruit of their own karma, they perform their karmas. Men do their karmas in the hope of a return. To experience this fruit of karma, man takes birth again. The reason is this: because he does karmas for the sake of their fruit, he has to live a human life again to experience the fruit of karma. So we must recognise that to do karmas without desire for the fruit is the chief duty. Here there are two kinds of karma. The Bhagavad Gītā has taught these as Dharmas, Svadharma and Paradharma. People take this Svadharma to concern only race, religion, caste and class. They believe too that this Svadharma is the highest good. But though it is indeed the highest good, it has nothing to do with race, religion and caste, as they imagine.