Short answers, pulled from the story.
The power source in Jujutsu Kaisen is called Cursed Energy which flows from negative emotions naturally existing within the human body. This energy accumulates to create malevolent spiritual entities known as Curses that manifest as grotesque monsters drawing on traditional Japanese folklore.
Yuji Itadori became the host of Ryomen Sukuna after swallowing a rotten finger talisman to protect Megumi Fushiguro who was tasked with retrieving it. This act made him the vessel for the powerful ancient sorcerer while allowing Satoru Gojo to postpone his execution until he consumes all twenty of Sukuna's fingers.
Jujutsu Kaisen was serialized in Shueisha's Weekly Shōnen Jump magazine from the 5th of March 2018 to the 30th of September 2024. The series concluded its run on that final date after releasing 30 individual volumes between the 4th of July 2018 and the 25th of December 2024.
Manga author Gege Akutami created Jujutsu Kaisen while drawing inspiration from Neon Genesis Evangelion horror films found footage movies and works by Yoshihiro Togashi Masashi Kishimoto and Yusuke Murata. Akutami stated that the magic system draws largely from Hunter × Hunter and fights reject emotional arguments according to the author's words.
The first season aired from the 3rd of October 2020 to the 27th of March 2021 with a second season running from July 6 to the 28th of December 2023 covering the Shibuya Incident arc. A prequel film premiered on the 24th of December 2021 while the third season covering the Culling Game arc began on the 9th of January 2026.