In plain words
These are the five yajñas, called Deva-yajña, Ṛṣi-yajña, Pitṛ-yajña, Manuṣya-yajña and Bhūta-yajña.
What is Deva-yajña? Is this fit and suited for ordinary people to perform? For this no altars of yajña need be built. No śāstras need be recited. No Vedas need be chanted by heart. Then in what way is this yajña to be performed? God dwells in the human body, in every atom and in every particle, as the One within. Such a Paramātma, as the very form of rasa, moves in every limb. In waking, dream and deep sleep He goes on guarding this body and nourishing it. So the whole of the body rests in God's protection alone. That is precisely why they held that to remember with gratitude the God who has protected us so, to worship Him and to honour Him, is itself Daiva-yajña. When someone in the world does us even a small help, we remember him with gratitude in many ways. In this modern age, if our towel falls down and someone hands it to us, we say Thanks with gratitude. Then should we not offer some kind of gratitude to the God who has protected our very life, made our very life flourish and nourished our very life! Those very prayers full of gratitude are these yajñas. To pray to God, no wealth and no place of any other kind are needed. The worship offered to Him with the heart's gratitude, the worship done with the sacred purity of thought, word and deed: these alone are His yajñas.
Ṛṣi-yajña. It is the ṛṣis who went on giving many kinds of commands, telling man with what aim he should enter this world, on what path, how he should foster a distinctive path, and how he should follow the right path in all his doings. In human life, from daybreak until we lie down, we take part in many kinds of karma. Which karma is to be done on what path, when, where and how: this is what the ṛṣis alone have given, the commands they have laid down. Precisely because they gave the commands that are the basis for living in this world, because they gave some kinds of zeal and encouragement for a life fit to be an ideal, to honour these ṛṣis and remember them in the right way is itself this Ṛṣi-yajña. These śāstras are treasures of nectar that they practised, experienced and then handed on. To go on doing the karmas the śāstras approve, bowing with gratitude to the ṛṣis who made the śāstras and honouring them: this is the debt to the ṛṣis. This itself is Ṛṣi-yajña.
Pitṛ-yajña. The root causes of our life and of our body are the mother and father alone.