prefatory chapter

Translations
вступительная глава
The book begins with a prefatory chapter that sets the context for the story.
Книга начинается с вступительной главы, которая задает контекст для истории.
Definitions
A prefatory chapter is an introductory section of a book or document that provides context, background information, or an overview of the content that follows. It often sets the tone for the work and may include acknowledgments, the author's intentions, or a summary of the main themes.