What is the difference between a challenge or banning?
A challenge is an attempt to remove or restrict materials, based upon the objections of a person or group. A banning is the removal of those 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.
[Taken from the American Library Association's website on Banned Books]
This map is drawn from cases documented by ALA and the Kids' Right to Read Project, a collaboration of the National Coalition Against Censorship and the American Booksellers Foundation for Free Expression. Details are available in ALA's "Books Banned and Challenged 2007-2008; 2008-2009; 2009-2010; and 2010-2011.