Supplier : fournisseur
A supplier is an individual or a company that supplies another company with products or raw materials. Almost no company can do everything itself, so it calls on the services of others to obtain what it needs.
Some companies are in the business of assembling rather that manufacturing. A good example is that of computer companies like ACER or DELL. These companies have a wide range of suppliers who provide them with the individual parts needed to build a computer. So their suppliers are Intel for processeurs, Invidia pour graphics cards, Microsoft for software etc.
Manufacturers also need companies to supply raw materials, like metal.
Office supplies : fournitures de bureau
Service providers : prestataires de service.
We don’t usually use the word supplier for companies that provide a service. Service providers may include catering (traiteurs), cleaning (nettoyage) or training (formation).