The RESTful API defines a set of common interactions (read, update, search, etc.) performed on a repository of resources. These interactions follow the RESTful paradigm of managing state by Create/Read/Update/Delete actions on a set of identified resources. While this approach solves many use cases, there is some functionality that can be met more efficiently using an Remove Procedure Call (RPC)-like paradigm, where named operations are performed with inputs and outputs (Execute). For more information on FHIR Operations see here.
The pages below provide an overview of the FHIR Operations the 1up FHIR server supports.