That is because Passover is not only remembered. It is staged through text at the table.
A Haggadah is the Passover seder book
Britannica defines the Haggadah as the special book containing the story of the Exodus as it must be retold at the beginning of the seder dinner on Passover.
This is the important distinction. The Haggadah is not a general prayer book or a Bible replacement. It is the script and interpretive guide for one of Judaism's central ritual meals.
It does more than narrate
Britannica notes that the Haggadah also supplies answers to the traditional questions asked by children at the seder.
That tells you what sort of book it is. The Haggadah is not merely informational. It is dialogic, ritual, and pedagogical.
The book turns memory into a shared act
Passover depends on retelling, but retelling in Judaism is rarely just narration. The Haggadah structures questions, blessings, symbols, and debate so that the Exodus becomes a lived exercise in collective memory.
Why it still matters
The Haggadah still matters because Jewish tradition refuses to leave liberation as an abstract idea. The story is put in a book designed for family, argument, and repetition.
The shortest accurate answer
A Haggadah is the book used at the Passover seder to retell the Exodus and guide the ritual order, questions, and meanings of the meal.