Short answers, pulled from the story.
The Sanskrit word pramana literally means proof. It derives from the root prama which combines a preposition meaning outward or forth with a term for measurement to indicate a process of acquiring correct knowledge.
Hinduism identifies six specific methods called pramanas as valid means to reach truths including perception known as Pratyaksha, inference termed Anumana, comparison and analogy called Upamana, postulation named Arthapatti, non-perception referred to as Anupalabdhi, and testimony defined as Sabda.
The Carvaka school accepted only one source of knowledge which was perception itself. It held all remaining methods as outright invalid or prone to error.
The two most important scholars of pramana were Dignaga and Dharmakirti who shaped the discipline through their writings. Dignaga's main text Pramana-samuccaya played a crucial role blending epistemology with logical discourse while Dharmakirti further developed these ideas in his Pramanavarttika influenced by Dignaga's work.
Dignaga introduced the idea of Apoha where recognition occurs by comparing and negating known objects from perception. General categories relate to differences from known objects rather than identification with universal truths so one knows a chariot is a chariot because it differs from things that are not chariots.