Anne was given her diary on her 13th birthday. She took it into hiding with her because she believed that it would “make the perfect friend and confidante.” She explains that she has never had any real friends and that her diary, named “Kittly” would be the “friend” to whom she could tell all of her feelings and thoughts. She did not know that her words would live on after her death, but "Kitty" helped her get through the long months she was in hiding.
Anne's diary is what most diaries are. It is a journal--a daily, or frequent--recording of her fears, anxieties, hatred, and hopes. As such, it provides an avenue for Anne to vent her feelings, a confessional, and a friend to whom she can confide. Surely this diary was extremely important to Anne in her confinement and isolation. In fact, it serves as a great example of the value that writing serves.
However, as Max Page writes in his criticism, the historical document that the diary of Anne Frank has become has been subjected to manipulation. First of all, Anne's own father deleted passages that pertained to Anne's records of sexual awakenings and her hatred for her mother. In the hands of movie-makers and playwrights, many of the records have been skewered to fit their motifs. And, finally, as Page points out, the use of this document for students to learn about the Holocaust is non-historical since the actual extermination of the Jews is not detailed by the very nature of the diary.