Short answers, pulled from the story.
The Pali word anattā means non-Self, indicating that no phenomenon possesses a permanent unchanging self or essence. Scholars like Peter Harvey note this term defines emptiness of Self rather than simple absence.
Nāgārjuna founded the Madhyamaka middle way school around 200 CE asserting no substantial entity exists called ātman self soul. Chapter 18 of his Mūlamadhyamakakārikā states no self-nature exists within any person.
Some first-millennium CE Buddhist texts suggest concepts implying self-like existence within tathāgatagarbha sutras appearing in the third century CE. Most scholars consider this doctrine equivalent to self contradicting vast majority anātman teachings yet some argue it expresses śūnyatā emptiness potentiality.
Hinduism Jainism and Buddhism all assert belief in rebirth emphasizing moral responsibility differently than pre-Buddhist materialistic philosophies like Charvaka school which claimed death ends everything without soul or rebirth. The Buddha condemned materialistic views encouraging moral irresponsibility while maintaining karmic fruition occurs without permanent essence.
Atman refers to essence human beings observing pure awareness witness-consciousness unaffected by ego distinct individual jivanatman embedded material reality. Peter Harvey notes negation temporal existents applied rigorously even more than Upanishads within Buddhism showing no such Atman exists evidence.