Final answer:
Apex calls to external Web services are known as Web service callouts and can be referred to as Web requests, Web services, API calls, or External calls depending on the context.
Step-by-step explanation:
Apex calls to external Web services are referred to as Web service callouts. These callouts allow Salesforce to communicate with outside systems using APIs. The callouts are often referred to by different terms depending on the context:
- Web requests when emphasizing the request-response mechanism,
- Web services when focusing on the service being accessed,
- API calls when discussing the programming interface being used, and
- External calls when highlighting the fact that the service is outside of the Salesforce platform.
In summary, while all these terms can be associated with communication to external services, API calls is the term that directly refers to the interaction between Salesforce (through Apex) and an external service.