Having suppliers registered is optional if you already have brands who directly supply you with their products. It all depends on your needs, but if your product supplier is not the same as the product brand, then you should make sure to have both registered in your system, and associated with each product.
In PrestaShop, a supplier is a company which provides you with a product. Even if you sell your own products, you must at least create your company as a supplier.
Just as for brands, your site's visitors can have rapid access to all of a supplier's products. This makes navigating around your site easier for them. In terms of visibility, filling out these fields will improve your position in search engines.
Click on "Add new supplier", and a creation form appears.
Fill out all of the fields:
Name. Indicate the name of the supplier in order to simplify your visitor's searches.
Description. Add a more complex description of your supplier and their activity and products. You can detail their specialties and promote the quality of their products. The supplier's description will be shown within your shop.
The contact details fields (Phone, Mobile phone, Address, Zip/postal code, City, Country). The State field only appears for relevant countries.
Logo. Having a supplier logo is essential: it leads the customers' eyes to trust your shop almost as much as they trust that supplier/brand.
Meta title. The title that will appear on the search engines when a request is made by a customer.
Meta description. A presentation of the supplier in just a few lines, intended to capture a customer's interest. This will appear in search results
Meta keywords. Keywords that you must define in order to have your site referenced by search engines. You can enter several of them, separated by commas, as well as expressions, which must be indicated in quotation marks.
Enable. You can disable a supplier, even temporarily. This will only remove it from the list of suppliers on your shop's front-end.
Save your changes in order to be taken back to the suppliers' list. From there, you can:
Click on a supplier's name or logo, and get all the products associated with it. If there are none, then you should work on a per-product basis, from the "Basic settings" tab of the "Products" page under the "Catalog" menu. The same result is achieved by clicking the view icon on the right.
Disable the supplier, by clicking on the green check-mark. Once disabled, a red cross appears in its place: click to re-enable the supplier.
View / Edit / Delete the supplier by clicking on the respective buttons on the right of the row.