In plain words
The man who weaves at the loom is the efficient cause. This is a silver tumbler. For it, the material cause is the silver. The goldsmith who made it is the efficient cause. But without the material cause or the efficient cause it could not have come to its proper form. So Bhāva-advaita means that we must try to recognise the oneness that is present in all. Cotton, thread and cloth, all three are one. This is Bhāva-advaita.
What is Kriyā-advaita? However many kinds of action we perform, it is through this sense of being the doer and the enjoyer, "I am doing, I have experienced, I have achieved," that man comes to separateness. Whatever work is done, whatever is achieved, however much is experienced, if all of it is for the pleasure of God, that is Karma-advaita. That is why, when you rest your feelings on God, however many actions you perform, they appear in the form of Advaita.
Then, Padārtha-advaita. This Padārtha-advaita is most important for the man of today. Every person, every creature too, is made of the five elements. In each person, sound is the form of space. Air is the form of our breathing in and breathing out. Heat is our temperature. Our sweat and urine, all of these are the form of water. Our whole body is the very form of earth. These five elements, are they not the form of the Paramātma! So every human being is made of these five elements, and so all are one. Whatever is in this body is in your body too. Whatever is in your body is in this body as well. These forms and names differ, but the substances are one. When we try to recognise such Padārtha-advaita, we can understand the Satya of ekovasi sarvabhūtāntarātma: the divinity in all is one. So the whole world is nothing but Advaita. Ekam eva advitīyaṃ brahma. There is no second at all. If we are to attain that principle, we must try to grasp well the teachings of our ancient ṛṣis. But unfortunately, because there are no people who give the right meaning of these Upaniṣads, these Brahma Sūtras or these Vedas, people fall into wrong meanings, multiply meanings of every kind, and forget the real meaning. Each goes on harmonising them as it occurs to him.
Embodiments of Prema! All of us must experience the principle that is full of Prema and share it. Those who teach today forget the Satya that the things they teach others apply to themselves too. They think, "We are teaching only the audience." So their teachings lose all value.