Magic systems are frameworks that define how magic operates within a fictional universe. They establish rules, limitations, and the source of magical power, which can vary widely from one story to another. For instance, in Brandon Sanderson's works, magic often has clear rules and consequences, making it a 'hard' magic system. These systems can enhance storytelling by creating tension and conflict, as characters navigate the boundaries of their magical abilities. They can also serve as a means of world-building, enriching the narrative with unique cultures and histories tied to the use of magic, such as in J.K. Rowling's Harry Potter series.