The Expense API can be used to create and send in expenses of different types on the behalf of a user. A user is a person that is employed in one or more organizations. An organization has configured the expense types, categories and fields that are applicable for the organization.
Findity has a white label app (iOS, Android and web) which can be styled according to the partners design. But the Expense API can also be used within the partners own applications to create expenses. This is done by using the OAuth endpoint to retrieve a token for a user and act on behalf of that users.