Introducing Selling Partner API
Selling Partner API (SP-API) is a modernized suite of REST APIs using standards that today's developers expect, while making it as simple as possible to migrate from our legacy Amazon Marketplace Web Service (Amazon MWS) APIs. SP-API includes all the functionality available in Amazon MWS plus many new APIs; including APIs for vendors. SP-API is available for all registered developers worldwide.
Private Developers
You can build applications for use with your own Amazon seller account. This requires you register as a developer.
Public Developers
You can build applications that sellers authorize and use to help manage their Amazon business. This requires you to register as a developer.
Amazon Selling Partner Appstore
You can publish your application in the Amazon Selling Partner Appstore, where Amazon sellers discover applications created by Amazon and public developers.