How are the seasons formatted in regards to the movie?
Visual
As mentioned above, the movie continues from the end of season 1. Season 2 is also a direct sequel to season 1, and you do not need to watch the movie before you watch season 2, as its first arc covers the exact same content as the movie. The second season's first cour is essentially an episodic rebroadcast of the movie, which then continues into the next arc (which was not in the movie) in its second cour.
Season 3 was announced on February 13, 2022, at the end of season 2's TV broadcast. It was recently confirmed to air in April 9 2023, with its first episode getting released with the last two episodes of the Entertainment District Arc as a pre-screening. It will be released in February 2023.
Breathing is a swordsmanship form used by the Demon Slayer Corps and allows the user to become stronger both physically and mentally by increasing the amount of oxygen in their body.
Demons become stronger by eating humans and can eventually develop supernatural powers called their Blood Demon Art. Each Blood Demon Art is different for every Demon.
The Demon Slayer Marks are mysterious markings that may appear on strong Demon Slayers. Some Demon Slayers are born with them, as well. The Demon Slayer Marks grant the Demon Slayer various abilities that are useful in battle, however, they also shorten the lifespan of the user.
The Hashira (or, Pillars) are the most powerful and top ranked warriors in the Demon Slayer Corps. There are nine members, and each Hashira uses a different breathing style.
The Twelve Kizuki (or, Twelve Demon Moons) are the twelve most powerful Demons who serve directly under Muzan Kibutsuji. Each member has received a larger portion of Muzan's blood, which has greatly strengthened their powers. The Twelve Kizuki are separated into two groups: the Upper Ranks and the Lower Ranks.