Suppliers gives you an overview of all the suppliers you have contract with on Marketplace.
To get to you suppliers page select "Contracts" on the top bar, then select "Suppliers" from the drop down list.
On the supplier page you have a list of the suppliers you have an active contract with on Marketplace. To get more information on the supplier select the supplier from the list.
On the supplier overview page you have information about the company and the contact information.
If you would like to add fields to your supplier report to be able to add some more information per contract, you can create your own custom fields that are only available on your suppliers for you information. Here on this link are more information on how to add custom fields to your suppliers.