Categories and tags
Two tabs: Categories and Tags. The list shows up to 500 rows with no paging. Each tab has a search box that filters by name or slug as you type; a matching sub-category shows with its parents, dimmed, so you can see where it sits.
Each category has a Name, a Slug (unique across all categories; Persian names make working Persian slugs), a plain-text Description, a Feature Image and a Parent. Use + Subcategory on a row to add a child.
Uncategorized
Uncategorized is a system category: it cannot be deleted or moved, but you can rename it and change its description and image. A product with no other category lands there.
Deleting
Delete a category and: products whose only category it was go to Uncategorized (as primary), its child categories move up to the root, and its product links are removed. A product with other categories just loses this one; if it was the primary, the deepest category it keeps becomes primary. A category cannot be its own parent or the parent of its own ancestor.
On the storefront
The category page is /store/category/slug. It lists products that belong directly to it, which is why ticking a category in the product editor also ticks its parents. Empty categories are hidden or shown by the store setting "Show categories with no products". Changing a category's slug redirects the old address to the new one.
Categories that are really brands
If you filed products under brand categories ("Laptops > Lenovo"), Brands → Convert to brands turns those categories into brands, can take the products out of them or delete them, and redirects each deleted category's page to its brand page. See Brands.
Tags
A tag has a name, slug and description. Deleting a tag has no in-use check; it just removes the tag from products.