Soya chunks are made using soy flour that has been 'defatted' or the oil is removed. They are the byproducts left after extracting soybean oil and have a rough texture when left dry. Soya chunks are also very versatile and can also be cooked to have a similar flavour as non-veg curries.
The literal translation of Dal Tadka is Dal=lentil and tadka=tempering. Tadka or chaunk (in hindi) is a term we often use in Indian cooking for the process of adding seasoning to a dish. It mostly involves adding spices like cumin seeds, mustard seeds, garlic, chilies, curry leaves etc. to hot oil or ghee.