That which gives us knowledge is known as pramana. What we experience through our sense organs is pratyaksha pramana. So seeing, hearing, feeling through the sense of touch etc., would all come under the category of pratyaksha pramana. Anumaana follows from pratyaksha pramana.
Suppose we see smoke emanating from behind a hill, we can guess that there is a fire somewhere behind that hill. That is because we know that smoke comes from a fire. But suppose we did not know the correlation between the two, we would not be able to make such a guess. In other words, we must learn to associate smoke and fire to conclude that smoke implies a fire. This conclusion which we come to, based on pratyaksha pramana, is anumaana. Then there is sabda pramana. The Vedas describe the Supreme One, said Velukkudi Krishnan, in a discourse. One cannot know Paramatma through pratyaksha pramana or anumaana. So suppose we had only the first two kinds of knowledge, we cannot know Him. In fact, without sabda pramana, one cannot even comprehend the nature of the atma. But the act of listening to the Vedas would not come under the category of pratyaksha pramana, though we use our faculty of hearing to hear the Vedas being recited, for the simple reason that merely listening to the Vedas being recited will not confer knowledge on us. We have to grasp the meaning of what is being recited. We can make a person say a few sentences in a language he is not familiar with. All he has to do is to parrot what we teach him. But that does not mean he understands the meaning of what he has been taught, or what he is saying. Likewise, one may listen to the Vedas being recited, but in the absence of understanding, of what use is the act of mere listening? Knowledge is not what is gained through our observations of the natural world; it is not what we experience in life; it is not knowing about the material aspects of life. True knowledge is knowledge that the atma is imperishable, and that for its liberation, we must seek the help of the Supreme One. We cannot attain moksha until we realise the difference between the body and the atma, and that the two are not interchangeable.