Short answers, pulled from the story.
The word Abhidharma appears in Buddhist texts dating from the 3rd century BCE. These writings contain detailed scholastic presentations of doctrine that differ sharply from colloquial suttas found elsewhere in the canon.
Theravada tradition identifies four categories: citta mind consciousness awareness, cetasika mental factors with fifty-two types, rūpa physical occurrences totaling twenty-eight types, and nibbana extinction which is unconditioned. Sarvastivada adds a fifth category called factors dissociated from thought to this list.
Buddhaghosa authored the Visuddhimagga Path of Purification in the 5th century CE. This comprehensive manual remains the main reference work for Theravada practice today.
The Sarvastivada Vaibhasika school dominated North India especially Kashmir and Gandhara regions. Their core text Jnana Prasthana Foundation of Knowledge was attributed to Kasyapa under Kushan Empire patronage.
Yogacara traditions evolved out of Sarvastivada Abhidharma incorporating eight consciousness theories. Asanga wrote the Yogacarabhumi Treatise on Foundation for Yoga Practitioners influenced heavily by earlier systems before Xuanzang translated Vijnaptimatrasiddhi Discourse on Perfection of Conscious-only into Chinese.