In plain words
In just the same way, on this journey through the field of karma, men are turning into fools who do not know the answer to the questions put to them by the people they meet here and there.
For this, in the Bhagavad Gītā (11:54), Kṛṣṇa Paramātma has given three important teachings in three words. (1) To know: oneself is one thing, the world another, Brahman another; one is not the body. Not the senses, not the mind and intellect: oneself is the very Ātma that fills all things. This you must come to know, whether from the lips of the guru, or through Viveka, Vairāgya and discernment, or through the true Jñāna reflected in a pure citta.
(2) To see: good mangoes are to be had in the market. If you know that, what comes of it? You must try to secure it and make it your own, mustn't you? (3) Then, to enter in truth: to savour the juice of its Ānanda, to become one with it, and, merged in it, to attain fullness.
Then that knower of Brahman turns into Brahman. This itself is the realisation of the Ātma: attaining Prakānti from Praśānti, and from Prakānti the Param Jyoti; the attainment of Mokṣa.