A data supplier (also called data provider) is a company that supplies raw data to other companies for any use they may have for it.
While there are many data supplier with the primary business of supplying data, there's a growing number of companies that become data suppliers as a side business or within partnership agreements with customers.
Companies that have established rigid intelligence / analytics / insights systems powered by external data, are now building their own data supply chain management. This way they make sure to have a steady stream of incoming data supplied by multiple data suppliers.