Rather sounds like a mystery novel doesn’t it? Actually, BISAC stands for Book Industry Standards and Communications which are the industry-standard codes used to organize books for booksellers, databases, and a source of information for Bookscan. An organization, the Book Industry Study Group (BISG), creates, maintains, and revises these codes of which there are currently over 3,000.
These industry-standard codes, make it easier for the bookseller to shelve the book in the appropriate section, choose the appropriate genre in a database which also makes it easier to do a search, and Bookscan uses it to help build their bestseller lists as well as track point of sale figures for all books.
AND, when provided by the author, it ensures that the book is categorized where the author intends it to be found.
As the author, you, well, your publisher must provide at least one BISAC code—the most general one which applies to your topic to the National Book Network (NBN). Ideally, three codes should be included. This allows you to fine tune the different marketing possibilities. The Tip Sheet Submission Form will give you as the author some ideas as to what your publisher will expect, or, if you’re self-publishing, what you should include on the back cover of your book.