Every operation available to the business layer can be accessed through a web API endpoint. These web API methods encapsulates calls to the business layer methods. Generated Web API methods can be accessed publicly and can act as a service to other clients (winforms, web forms, other api or service like a wcf app, mobile app, etc). You can also build a desktop app that can access the same API your ASP.NET Core app is using through the Web API. Clients of the Web API does not have to be a windows program, it returns collections as JSON data, or you can pass it JSON data when saving a new record or updating an existing record. Unlike the business layer, you can make it available publicly, say to other companies to access?