> ## Documentation Index > Fetch the complete documentation index at: https://docs.tied.com/llms.txt > Use this file to discover all available pages before exploring further. # Categories and structure > Organising and ordering articles. A category is the shelf. It groups articles inside one portal, and unlike articles, categories can nest inside each other. ## Nesting Every category can have a parent category and, through that same relationship, its own sub-categories. There's no fixed depth limit in the model — a category can sit under a category that sits under another one. The model allows deep nesting. Your readers will thank you for not using it. Two levels — a category and its sub-categories — covers almost every real Help Center. A sub-category earns its place when a category gets crowded, not before: if you can't list five articles that belong under a proposed sub-category today, fold it back into the parent until you can. ## Ordering Categories carry a position, and the default list order is ascending by that value. Moving a category up or down in the list is the same operation as changing its position — there's no separate "priority" or "featured" flag to reach for. ## Related categories Nesting says "this belongs inside that." Related categories say something different: "someone reading this probably also wants that" — without making one the parent of the other. A category can link to other categories independent of its place in the tree. Use it to cross-reference — "Billing" and "Refunds" are both worth surfacing from each other even though neither is a sub-category of the other. ## Locale is part of the identity Every category has a locale, and it must be one your portal already allows (see [Locales and translations](/help-center/locales)). A category's slug only has to be unique within its own portal *and* locale, which is what makes translation possible: the French and English versions of "Billing" are two separate category rows, sharing a slug, linked together as translations rather than fighting over it. ## Where articles land An article can belong to one category, or none. A categorized article inherits that category's locale automatically. An uncategorized article falls back to the portal's default locale instead — it doesn't stay locale-less. ## Next The editor, draft state, authorship and SEO. The root-and-associated model, for both categories and articles. Where categories live. Search, visibility and theming. This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.