What is a banned book?

This is what Banned Books looks like folks: "Iranian author and filmmaker Majid Barzegar announced on his Instagram account that his two recent novels, both previously approved for publication and printed by Cheshmeh Publishing, have been seized and banned from further production and distribution." (Iran Wire)

Banning is not that silly self-serving advertisement from the American Library Association in October so a tax supported agency can make you afraid to speak up. ALA doesn't want you to criticize bad books and other media that libraries spend your money on