In a category, customers see the first few products first, so the order matters. It is set by two things: the position of each product in the category and the category's default sorting.
Product position in a category
Catalog › Categories › (category) › Products in Category
Click the category in the tree and expand the Products in Category section.
Enter a number in the Position column for the products. A lower number comes first: 1 is first. Products without a number (0) come before all the others.

Position - a lower number means a higher place in the category. Click Save.
Default sorting of a category
In the same category, expand Display Settings.

- Anchor - Yes also shows products from subcategories.
- Available Product Listing Sort By - which sorting options the customer has.
- Default Product Listing Sort By - the sorting used when the category opens.
For Default Product Listing Sort By, untick Use Config Settings and choose Position (your manual order), Product Name or Price.
For Available Product Listing Sort By, leave Use All so customers can change the sorting themselves.
The setting for all categories at once is in Stores › Configuration › Catalog › Catalog › Storefront › Product Listing Sort by. A category with its own setting overrides it.
Products from subcategories (Anchor)
A category with Anchor = Yes also shows all products from its subcategories, not just those added to it directly. These products are sorted by the position they have in their own subcategory, so the order in the parent category can look mixed up. If you want an exact order in the parent category, add the products to it directly as well and give them a position there.
Common problems
I changed the position, but the shop still shows the old order
Check that Position is selected in Default Product Listing Sort By. Then flush the cache; after bigger changes the order updates within a few minutes, once the index has been rebuilt.
A new product always comes first
Its position is 0. Give it a number higher than the products that should come before it.
The order is different on the home page or in search
Position only applies within the category. Search sorts by relevance, and the home page by the settings of the block or module.


