Wikipedia:Categories are different from articles

Categories and articles serve different purposes in Wikipedia. Where articles are meant to be the main direct source of informative content that readers spend the majority of their time reading, categories are meant to be a navigational system that helps readers quickly move from one related article to another within a related subject area. Articles are meant to support detailed discussions on a particular topic, while categories are ideally streamlined indexes that can point readers to the discussions they want.

Historically, Wikipedia policies and guidelines (with the exception of Overcategorization) were developed as if all the rules which could apply to articles could apply equally well to categories. But, as described in the previous paragraph, categories and articles are fundamentally different and therefore have different requirements for what are considered accepted practices and structure.

Categorization provides useful guidelines for category creation, while Overcategorization provides guidelines for categories that should not be created or should be considered for removal. Category deletion policy primarily gives guidance for criteria for the speedy deletion of certain types of categories.

Applying rules tailored for Articles for deletion, such as the Deletion policy or the Arguments to avoid in deletion discussions essay, to deletion debates at Categories for discussion without considering the fundamentally different nature of what is being discussed may give unexpected results. Below are some examples of differences between article policies and category policies.
 * Verifiability and references Ideally all information in articles should be verifiable and properly referenced. Categories themselves do not contain references and therefore validating references must appear in the articles themselves.  Articles should ultimately only be categorized according to verifiable, referenced information within themselves; that is the only way to actually prove that an article in a category actually belongs there.
 * Lack of bias Articles should be unbiased and presented from a neutral point of view. In a similar fashion, criteria for category inclusion should be something that a reasonable editor can objectively determine based on information presented in the article.  Categories which inherently rely on overly subjective inclusion criteria are inappropriate because including something in a category is a black-and-white presentation.  A category does not have the luxury of going into subtle details about whether an article belongs there or not, and therefore readers must be able to have a high degree of faith that when an article appears in a category its presence is not debatable.


 * Occasionally you will find articles about a subject that, while acceptable as a general topic of discussion, is not acceptable as a criterion for category inclusion. An example is the article Cult film. The general discussion of the phenomenon of "cult films" is valid, but unfortunately it is not objectively possible to say whether specific individual films are "cult films".  Thus creating "Category:Cult films" to list specific films that have cult status would be unacceptable as it would rely in large part on individual editorial bias for determining the cult status of its film article entries.


 * List articles versus categories As a rule of thumb, if something is acceptable as a category it is probably also acceptable as a list article. The reverse is not true, however, and there are many topics that work well as list articles but that do not work well as categories.  Overcategorization provides examples of some such topics, such as lists being acceptable for the cast list of a film but a category for that purpose not being necessary.