Chicago manual style citations are used when covering history, art, and literature. Purdue Owl's manual of the Chicago manual style will help explain what this citation method is used for and the proper way to use this style.
MLA citations are used for the humanities, such as English and communications. Purdue Owl's manual of MLA citations will explain the proper usage of this citation.
APA citation is used for education, medical papers, health, science, social sciences, and business. Purdue Owl's manual for APA citation will help explain the proper usage of this citation.