Short answers, pulled from the story.
Pramana literally means proof and refers to a reliable and valid means by which human beings gain accurate, true knowledge. The word is rooted in pramā, built from the Sanskrit root pra, meaning outward or forth, and mā, meaning measurement.
Many ancient and medieval Indian texts identify six pramanas as correct means of accurate knowledge: Pratyaksha, Anumana, Upamana, Arthapatti, Anupalabdhi, and Shabda. Earlier texts varied on the count; the Taittiriya Aranyaka lists only four, while Vedvyasa discusses as many as ten and Krtakoti proposes eight.
Buddhism accepts only two pramanas as valid means to knowledge: Pratyaksha, perception, and Anumana, inference. The scholar Rinbochay notes that Buddhism also treats scripture, including the words of Buddha and other valid persons and valid minds, as a third source, though this is considered a form of perception and inference.
The Charvaka school, part of the Sramana tradition, accepts only one pramana as reliable: perception. It holds all other means of knowledge as either invalid outright or too prone to error to trust.
Dignaga and Dharmakirti are considered the two most important scholars of pramana in Buddhism. Dignaga wrote the Pramana-samuccaya and introduced the concept of Apoha, while Dharmakirti, influenced by Dignaga, developed these ideas further in his text the Pramanavarttika.
Anumana is inference, reaching a new conclusion from observation and prior truth, such as inferring fire from observed smoke. Upamana is comparison and analogy, such as identifying an unfamiliar animal by comparing it to a familiar one like a cow.