Banned Books Week was launched in 1982 in response to a sudden surge in the number of challenges to books in libraries, bookstores, and schools. By focusing on efforts to remove or restrict access to books, Banned Books Week draws national attention to the harms of censorship. The annual event highlights the value of free and open access to information and brings together the entire book community — librarians, educators, authors, publishers, booksellers, and readers of all types — in shared support of the freedom to seek and to express ideas. -- ALA Banned Books Week
Challenge: An attempt to remove or restrict materials, based upon the objections of a person or group.
Ban: Removal or restriction of materials.
"Challenges do not simply involve a person expressing a point of view; rather, they are an attempt to remove material from the curriculum or library, thereby restricting the access of others. Due to the commitment of librarians, teachers, parents, students and other concerned citizens, most challenges are unsuccessful and most materials are retained in the school curriculum or library collection." -- ALA About Banned & Challenged Books