Why does it go to all this trouble to find when to use a BRIN index without even expanding on the name of it? "Chapter 71. BRIN Indexes"[0] > BRIN stands for

Why does it go to all this trouble to find when to use a BRIN index without even expanding on the name of it? "Chapter 71. BRIN Indexes"[0] > BRIN stands for Block Range Index. BRIN is designed for handling very large tables in which certain columns have some natural correlation with their physical location within the table. [0] https://www.postgresql.org/docs/current/brin-intro.html https://www.postgresql.org/docs/current/brin-intro.html